- Purpose of This PDQ Summary
- Prostate Cancer Susceptibility Loci
- Polymorphisms and Prostate Cancer Susceptibility
- Interventions in Familial Prostate Cancer
- Prostate Cancer Risk Assessment
- Psychosocial Issues in Prostate Cancer
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- Changes to This Summary (12 / 03 / 2009)
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Genetics of Prostate Cancer (PDQ®): Genetics - Health Professional Information [NCI]
This information is produced and provided by the National Cancer Institute (NCI). The information in this topic may have changed since it was written. For the most current information, contact the National Cancer Institute via the Internet web site at http://cancer.gov or call 1-800-4-CANCER
Genetics of Prostate Cancer
Purpose of This PDQ Summary
This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the genetics of prostate cancer. This summary is reviewed regularly and updated as necessary by the Cancer Genetics Editorial Board.
The following information is included in this summary:
- Family history and other risk factors for prostate cancer.
- Prostate cancer susceptibility loci and polymorphisms associated with prostate cancer risk.
- Risk assessment for hereditary prostate cancer.
- Screening and risk modification for hereditary prostate cancer.
- Psychosocial issues associated with hereditary prostate cancer.
The summary also contains level-of-evidence designations. These designations are intended to help readers assess the strength of the evidence in relation to specific studies or strategies. A description of how level-of-evidence designations are made is described in detail in the PDQ summary Cancer Genetics Overview.
This summary is intended to provide clinicians a framework for discussing genetic testing, screening, and risk modification options with individuals at risk for hereditary prostate cancer, as well as for making referrals to cancer risk counseling services. It does not provide formal guidelines or recommendations for making health care decisions. Information in this summary should not be used as a basis for reimbursement determinations.
Many of the medical and scientific terms used in this summary are found in the NCI Dictionary of Genetics Terms. When a linked term is clicked, the definition will appear in a separate window.
Many of the genes described in this summary are found in the Online Mendelian Inheritance in Man (OMIM) database. When OMIM appears after a gene name or the name of a condition, click on OMIM for a link to more information.
The public health burden of prostate cancer is substantial. A total of 192,280 new cases of prostate cancer and 27,360 deaths from the disease are anticipated in the United States in 2009, making it the most frequent nondermatologic cancer among U.S. males. A man's lifetime risk of prostate cancer is 1 in 6. Prostate cancer is the second leading cause of cancer death in men, exceeded only by lung cancer.
Some men with prostate cancer remain asymptomatic and die from unrelated causes rather than as a result of the cancer itself. This may be due to the advanced age of many men at the time of diagnosis, slow tumor growth, or response to therapy. The estimated number of men with latent prostate carcinoma (i.e., prostate cancer that is present in the prostate gland but never detected or diagnosed during a patient's life) is greater than the number of men with clinically detected disease. A better understanding is needed of the genetic and biologic mechanisms that determine why some prostate carcinomas remain clinically silent, while others cause serious, even life-threatening illness.
Prostate cancer exhibits tremendous differences in incidence among populations worldwide; the ratio of countries with high and low rates of prostate cancer ranges from 60-fold to 100-fold. Asian men typically have a very low incidence of prostate cancer, with age-adjusted incidence rates ranging from 2 to 10 per 100,000 men. Higher incidence rates are generally observed in northern European countries. African American men, however, have the highest incidence of prostate cancer in the world; within the United States, African American men have a 60% higher incidence rate compared with white men.
These differences may be due to genetic, environmental, and social influences (such as access to health care), which affect the development and progression of the disease. Differences in screening practices have also had a substantial influence on prostate cancer incidence, by permitting prostate cancer to be diagnosed in some patients before symptoms develop or before abnormalities on physical examination are detectable. An analysis of population-based data from Sweden suggested that a diagnosis of prostate cancer in one brother leads to an early diagnosis in a second brother using prostate-specific antigen (PSA) screening. This may account for an increase in prostate cancer diagnosed in younger men that was evident in nationwide incidence data. A genetic contribution to prostate cancer risk has been documented, but knowledge of the molecular genetics of prostate cancer is still limited. Malignant transformation of prostate epithelial cells and progression of prostate carcinoma are likely to result from a complex series of initial and promotional events under both genetic and environmental influences.
Risk Factors for Prostate Cancer
The three most important recognized risk factors for prostate cancer in the United States are:
- Family history of prostate cancer.
Age is an important risk factor for prostate cancer. Prostate cancer is rarely seen in men younger than 40 years; the incidence rises rapidly with each decade thereafter. For example, the probability of being diagnosed with prostate cancer is 1 in 19,299 for men younger than 40 years, 1 in 45 for men aged 40 through 59 years, and 1 in 7 for men aged 60 through 79 years, with an overall lifetime risk of developing prostate cancer of 1 in 6.
Endogenous hormones, including both androgens and estrogens, likely influence prostate carcinogenesis. It has been widely reported that eunuchs and other individuals with castrate levels of testosterone prior to puberty do not develop prostate cancer. Some have speculated that higher serum levels of testosterone and lower levels of estrogen result in higher rates of prostate cancer, but this has not been consistently demonstrated in clinical studies. Some investigators have considered the potential role of genetic variation in androgen biosynthesis and metabolism in prostate cancer risk, including the potential role of the androgen receptor CAG repeat length in exon 1.
Some dietary risk factors may be important modulators of prostate cancer risk; these include fat and/or meat consumption, vitamin E,[11,12] lycopene,[12,13] dairy products/calcium/vitamin D, and selenium. Phytochemicals are plant-derived nonnutritive compounds, and it has been proposed that dietary phytoestrogens may play a role in prostate cancer prevention. For example, Southeast Asian men typically consume soy products that contain a significant amount of phytoestrogens; this diet may contribute to the low risk of prostate cancer in the Asian population. There is little evidence that alcohol consumption is associated with the risk of developing prostate cancer; however, data suggest that smoking increases the risk of fatal prostate cancer. Several studies have suggested that vasectomy increases the risk of prostate cancer, but other studies have not confirmed this observation.
Refer to the PDQ summary on Prevention of Prostate Cancer for more information.
Family History as a Risk Factor for Prostate Cancer
As with breast and colon cancer, familial clustering of prostate cancer has been reported frequently.[20,21,22,23,24] From 5% to 10% of prostate cancer cases are believed to be due primarily to high-risk inherited genetic factors or prostate cancer susceptibility genes. Results from several large case-control studies and cohort studies representing various populations suggest that family history is a major risk factor in prostate cancer.[21,25,26] A family history of a brother or father with prostate cancer increases the risk of prostate cancer, and the risk is inversely related to the age of the affected relative.[22,23,24,25,26]
Although many of the prostate cancer studies examining risks associated with family history have used hospital-based series, several studies described population-based series. The latter are thought to provide information that is more generalizable. The Massachusetts Male Aging Study of 1,149 Boston-area men found a relative risk (RR) of 3.3 (95% confidence interval [CI] of 1.8–5.9) for prostate cancer among men with a family history of the disease. This effect was independent of environmental factors, such as smoking, alcohol use, and physical activity. Further associations between family history and risk of prostate cancer were characterized in an 8-year to 20-year follow-up of 1,557 men aged 40 through 86 years who had been randomly selected as controls for a population-based case-control study conducted in Iowa from 1987 through 1989. At baseline, 4.6% of the cohort reported a family history of prostate cancer in a brother or father, and this was positively associated with prostate cancer risk after adjustment for age (RR = 3.2; 95% CI, 1.8–5.7) or after adjustment for age, alcohol, and dietary factors (RR = 3.7; 95% CI, 1.9–7.2).
A meta-analysis of 33 epidemiologic studies provides more detailed information regarding risk ratios related to family history of prostate cancer. Risk appears to be greater for men with affected brothers (RR = 3.4; 95% CI, 3.0–3.8) than for men with affected fathers (RR = 2.2; 95% CI, 1.9–2.5). Although the reason for this difference in risk is unknown, possible hypotheses include X-linked or recessive inheritance. In addition, risk increased with increasing numbers of affected close relatives: RR was 2.6 (95% CI, 2.3–2.8) for one first-degree relative and 5.1 (95% CI, 3.3–7.8) for two or more first-degree relatives, but RR was only 1.7 (95% CI, 1.1–2.6) for an affected second-degree relative. Risk was influenced by age at prostate cancer diagnosis in this meta-analysis: RR was 3.3 (95% CI, 2.6–4.2) for diagnosis before age 65 years, versus a RR of 2.4 (95% CI, 1.7–3.6) for diagnosis at age 65 years or older.
Among the many data sources included in this meta-analysis, those from the Swedish population-based Family Cancer Database warrant special comment, as they are derived from a resource that contains 10.2 million individuals, among whom there are 182,000 fathers and 3,700 sons with medically verified prostate cancer. The size of this data set, with its near complete ascertainment of the entire Swedish population and objective verification of cancer diagnoses, should yield risk estimates that are both accurate and free of bias. The familial standardized incidence ratios (SIRs) for prostate cancer were 2.4 (95% CI, 2.2–2.6), 3.8 (95% CI, 2.7–5.0), and 9.4 (95% CI, 5.8–14.0) for men with prostate cancer in their fathers only, brothers only, and both father and brother, respectively. The SIRs were even higher if the affected relative was diagnosed with prostate cancer before age 55 years. A separate analysis of this Swedish database reported that the cumulative (absolute) risks of prostate cancer among men in families with two or more affected cases were 5%, 15%, and 30% by ages 60, 70, and 80 years, respectively, compared with 0.45%, 3%, and 10% at the same ages in the general population. The risks were higher still if the affected father was diagnosed before age 70 years. The corresponding familial population attributable fractions (PAFs) were 8.9%, 1.8%, and 1.0% for the same three groups, respectively, yielding a total PAF of 11.6%; approximately 11.6% of all prostate cancer in Sweden can be accounted for on the basis of these familial risk factors.
Table 1. Relative Risk Related to Family History of Prostate Cancer
|Risk Group||Relative Risk for Prostate Cancer|
|Brother with prostate cancer diagnosed at any age||3.4 (95% CI, 3.0–3.8)|
|Father with prostate cancer diagnosed at any age||2.2 (95% CI, 1.9–2.5)|
|One affected first-degree relative diagnosed at any age||2.6 (95% CI, 2.3–2.8)|
|One affected second-degree relative diagnosed at any age||1.7 (95% CI, 1.1–2.6)|
|Affected first-degree relative(s) diagnosed age <65 years||3.3 (95% CI, 2.6–4.2)|
|Affected first-degree relative(s) diagnosed age >65 years||2.4 (95% CI, 1.7–3.6)|
|Two or more affected first-degree relatives diagnosed at any age||5.1 (95% CI, 3.3–7.8)|
The risk of prostate cancer may also increase in men who have a family history of breast cancer. Approximately 9.6% of the Iowa cohort had a family history of breast and/or ovarian cancer in a mother or sister at baseline, and this was positively associated with prostate cancer risk (age-adjusted RR = 1.7; 95% CI, 1.0–3.0; multivariate RR = 1.7; 95% CI, 0.9–3.2). Men with a family history of both prostate and breast/ovarian cancer were also at increased risk of prostate cancer (RR = 5.8; 95% CI, 2.4–14.0). Other studies, however, did not find an association between family history of female breast cancer and risk of prostate cancer.[27,32] A family history of prostate cancer also increases the risk of breast cancer among female relatives. The association between prostate cancer and breast cancer in the same family may be explained, in part, by the suggested increase in the risk of prostate cancer among men with BRCA1/2mutations in the setting of hereditary breast/ovarian cancer.[34,35] (Refer to the BRCA1 and BRCA2 subsection of the Prostate Cancer Susceptibility Loci section of this summary for more information.)
Family history has been shown to be a risk factor for men of different races and ethnicities. In a population-based case-control study of prostate cancer among African Americans, whites, and Asian Americans in the United States and Canada (Los Angeles, San Francisco, Hawaii, Vancouver, and Toronto), 5% of controls and 13% of all cases reported a father, brother, or son with prostate cancer. These prevalence rates were somewhat lower among Asian Americans as compared with African Americans or whites. A positive family history was associated with a twofold to threefold increase in risk in each of the three ethnic groups. The overall odds ratio associated with a family history of prostate cancer was 2.5 (95% CI, 1.9–3.3) with adjustment for age and ethnicity.
Evidence for inherited forms of prostate cancer can be found in several U.S. and international studies.[21,25,37,38,39,40] It was first noted in 1956 that men with prostate cancer reported a higher frequency of the disease among relatives than did controls. Shortly thereafter, it was reported that deaths from prostate cancer were increased among fathers and brothers of men who died of prostate cancer versus controls who died of other causes.
Refer to the PDQ Prevention of Prostate Cancer summary for more information about risk factors for prostate cancer in the general population.
Inheritance of Prostate Cancer Risk
Many types of epidemiologic studies (case control, cohort, twin, family) strongly suggest that prostate cancer susceptibility genes exist in the population. An analysis of monozygotic and dizygotic twin pairs in Scandinavia concluded that 42% (CI, 29%–50%) of prostate cancer risk may be accounted for by heritable factors. This is in agreement with a previous U.S. study that showed a concordance of 7.1% between dizygotic twin pairs compared with a 27% concordance between monozygotic twin pairs. The first segregation analysis was performed in 1992 using families from 740 consecutive probands who had radical prostatectomies between 1982 and 1989. The study results suggested that familial clustering of disease among men with early-onset prostate cancer was best explained by the presence of a rare (frequency of 0.003) autosomal dominant, highly penetrantallele(s). Hereditary prostate cancer susceptibility genes were predicted to account for almost half of early-onset disease (age 55 years or younger).
Subsequent segregation analyses generally agreed with the conclusions but differed in the details regarding frequency, penetrance, and mode of inheritance.[45,46,47] A study of 4,288 men who underwent radical prostatectomy between 1966 and 1995 found that the best fitting genetic model of inheritance was the presence of a rare, autosomal dominant susceptibility gene (frequency of 0.06). In this study, the lifetime risk for carriers was estimated to be 89% by age 85 years compared with 3.9% for noncarriers. This study also suggested the presence of genetic heterogeneity, as the model did not reliably predict prostate cancer risk in first-degree relatives of probands who were diagnosed at age 70 years or older. More recent segregation analyses have concluded that there may be multiple genes associated with prostate cancer [48,49,50,51] in a pattern similar to other adult-onset hereditary cancer syndromes, such as those involving the breast, ovary, colorectum, kidney, and melanoma. In addition, a segregation analysis of 1,546 families from Finland found evidence for Mendelian recessive inheritance. Results showed that individuals carrying the risk allele were diagnosed with prostate cancer at younger ages (<66 years) compared with noncarriers. This is the first segregation analysis to show a recessive mode of inheritance.
Prostate Cancer Susceptibility Loci
Like most cancers, prostate cancer is a complex neoplastic disorder in which disease initiation is the result of an interaction between genetic and nongenetic factors. The identification of causative genes for prostate cancer, however, has been elusive in spite of segregation analyses of prostate cancer families that support the existence of one or more hereditary prostate cancer genes.[1,2,3,4,5,6,7,8] Several candidate loci have been identified by performing genome-wide linkage analysis studies in high-risk families, but confirmation of these proposed susceptibility loci from subsequent studies has often been lacking. Further, some prostate cancer susceptibility genes have been characterized by positional cloning, but follow-up studies have not yet demonstrated that any of these loci contribute to a significant number of high-risk prostate cancer families. While the goal of linkage analysis is to identify the chromosomal location of prostate cancer susceptibility genes, none of the putative genes in these regions identified to date have been widely accepted as clinically useful. Examples of loci that have been identified in studies of high-risk families are discussed below and are summarized in Table 2.
Prostate Cancer Linkage Studies
The recognition that prostate cancer clusters within families has led many investigators to collect multiplex families with the goal of localizing prostate cancer susceptibility genes through linkage studies. Despite the extensive collection of prostate cancer families and the formation of a collaborative research group (the International Consortium for Prostate Cancer Genetics [ICPCG]), the identification of prostate cancer genes has been exceedingly difficult. A review of eight prostate cancer linkage studies that evaluated a total of 4,600 cases of prostate cancer from 1,293 kindreds found several methodological differences. The authors suggest that differences in populations, enrollment criteria, and underlying genetic models used for each analysis may account for the lack of consistency between linkage studies. The following discussion highlights both the clinical and research issues leading to this complexity.
Linkage studies are typically performed on high-risk extended families in which multiple cases of a particular disease have occurred in an effort to identify disease susceptibility genes. Linkage analysis statistically compares the genotypes between affected and unaffected individuals, and looks for evidence that known genetic markers are inherited along with the disease trait. If such evidence is found (linkage), it provides statistical data that the chromosomal region near the marker also harbors a disease susceptibility gene. Once a genomic region of interest has been identified through linkage analysis, additional studies are required to prove that there truly is a susceptibility gene at that position. The statistical power of linkage analysis is affected by:
- Family size and having a sufficient number of family members who volunteer to contribute DNA.
- The number of disease cases in each family.
- Factors related to age at disease onset.
- Gender differences in disease risk.
Because the risk of prostate cancer is influenced by both age at onset in affected relatives and number of relatives affected, the lack of accurate family history information about prostate cancer can limit the overall analysis.
Because a standard definition of hereditary prostate cancer (HPC) has not been accepted, prostate cancer linkage studies have not used consistent criteria for enrollment. One criterion that has been proposed is the Hopkins Criteria that provides a working definition of HPC families. The three criteria are kindreds with prostate cancer in the following:
|1.||Three or more first-degree relatives (father, brother, son),|
|2.||Three successive generations of either the maternal or paternal lineages, and/or|
|3.||At least two relatives affected at age 55 years or younger.|
Families need to fulfill only one of these criteria to be considered to have HPC. Validity of these research criteria has not been confirmed for clinical management and must await identification of specific prostate cancer susceptibility genes. Using these criteria, a study has shown that approximately 5% of men in a large surgical series will be from a family with HPC.
An additional issue in linkage studies is the high background rate of sporadic prostate cancer in the context of family studies. As a man's lifetime risk of prostate cancer is 1 in 6, it is possible that families under study have men with both inherited and sporadic prostate cancer. Thus, men who do not inherit the prostate cancer susceptibility gene that is segregating in their family may still develop prostate cancer. Currently there are no clinical or pathological features of prostate cancer that will allow differentiation between inherited and sporadic forms of the disease. Similarly, there are no definitive data regarding the clinical phenotype or natural history of prostate cancer associated with specific candidate loci. Measurement of the serum prostate-specific antigen (PSA) has been used inconsistently in evaluating families used in linkage analysis studies of prostate cancer. In linkage studies, the definition of an affected man can be biased by the use of serum screening as the rates of prostate cancer in families will differ between screened and unscreened families.
In an effort to clarify the inconsistent linkage results, the ICPCG combined genome-wide linkage data from 1,233 families contributed by ten individual research teams. One analytic approach used the entire set of 1,233 families and five regions of suggestive linkage (logarithm of the odd [LOD] scores between 1.87 and 3.30) were identified: 5q12, 8p21, 15q11, 17q21, and 22q12. Therefore, the pooled analysis did not formally confirm any previously identified chromosomal regions of interest (see below). In the hope that targeting more homogenous family subsets might facilitate gene identification, a second analysis focused on subsets of the 1,233 families sharing common features, such as multiple affected family members or younger age at diagnosis. In 269 families with at least five affected members, significant linkage was detected at 22q12 (LOD score 3.57) and suggestive linkage was also observed at 1q25, 8q13, 13q14, 16p13, and 17q21. In 606 families with members aged 65 years or younger at diagnosis, linkage was suggested at 3p24, 5q35, 11q22, and Xq12. These findings may facilitate prioritization of genomic regions for further study.
One way to address the inconsistency between linkage studies is to require inclusion criteria that defines clinically significant disease (e.g., Gleason grade =7, PSA =20 ng/mL) in an affected man.[13,14,15] This approach attempts to define a homogeneous set of cases/families to increase the likelihood of identifying a linkage signal. It also prevents the inclusion of cases that may be considered clinically insignificant that were identified by screening in families.
Investigators have also incorporated clinical parameters into linkage analyses with the goal of identifying genes that may influence disease severity.[16,17] This type of approach, however, has not yet led to the identification of consistent linkage signals across datasets.[18,19]
Hereditary Prostate Cancer 1
The results of a genome-wide scan of 91 high-risk prostate cancer families meeting the Hopkins criteria from the United States and Sweden suggested the presence of a major prostate cancer susceptibility locus at chromosome 1q24, designated HPC1. Assuming genetic heterogeneity (i.e., that it is likely that only a subset of these 91 families carry an HPC1mutation), the odds favoring the presence of this gene are nearly 1 million to 1. The genetic evidence supporting the existence of HPC1 was confined to 35% of the 91 families. This subgroup was characterized clinically by having more than five affected family members and an average age at prostate cancer diagnosis younger than 65 years. Further analyses of families that are genetically linked to HPC1 revealed the following characteristics:
- Younger age at diagnosis.
- Higher tumor grade (Gleason score).
- More advanced stage at diagnosis.[21,22]
Despite the strength of the initial results, subsequent studies have often failed to confirm the linkage.[23,24,25,26] Nevertheless, confirmatory results were obtained in two studies in the United States that involved 59 and 92 families.[27,28] Linkage evidence in these reports was stronger among families in which prostate cancer was diagnosed earlier in life (<67 years) or that fit the Hopkins definition of HPC. In an analysis of 41 families from Utah, in which the mean number of affected men per family was large (10.7), linkage with 1q24-25 was confirmed. The ICPCG pooled data from 772 families in North America, Australia, Finland, Norway, Sweden, and the United Kingdom, and obtained some evidence of linkage at 1q24. The estimated percentage of familial prostate cancer families explained on the basis of this putative gene locus was 6%. Stronger evidence of linkage was seen among families with a male-to-male pattern of inheritance. Modest evidence for linkage to this region was also identified on a genome-wide scan of 188 families from Johns Hopkins, including 51 kindreds examined in the initial positive linkage study. A study of 33 African American families demonstrated some evidence in support of prostate cancer linkage to markers that map to several HPC candidate regions.
Data suggest that the RNASEL gene at 1q25 may be the molecular basis of the prostate cancer susceptibility locus HPC1. The gene encodes an endoribonuclease that is a member of the interferon-regulated 2-5A system. The recognition that RNASEL was both a candidate prostate cancer susceptibility gene and a gene involved in host resistance to viral infection led investigators to seek the presence of viral genomic sequences in prostate cancer tissue from multiple-case families linked to this locus. This work led to the identification of a novel human retrovirus, designated xenotropic murine leukemia virus-related virus (XMRV). Although this observation has stimulated additional research, the role of this viral agent in prostate carcinogenesis remains uncertain.
DeleteriousgermlineRNASEL mutations were detected in two of eight families with prostate cancer linkage to 1q24-25 markers. Follow-up studies by several groups, however, have not identified a significant number of RNASEL germline variants among families with HPC.[35,36] In a study of Finnish men with prostate cancer, a stop mutation, E265X, was found in 4.3% of the men from HPC families compared with 1.8% of controls. A founder frameshift mutation in RNASEL (471delAAAG) was identified in 4% of Ashkenazi individuals. The frequency of this mutation was higher in men with prostate cancer than in elderly male controls (6.9% vs. 2.4%, odds ratio [OR] = 3.9; 95% confidence interval [CI], 0.6–15.3; P = .17). Significant associations were noted between the common RNASELpolymorphism R462Q and familial prostate cancer. This substitution results in a threefold reduction in RNASEL activity. A Swedish population-based case-control study examined the prevalence of E265X and other variants in the RNASEL gene. There were no differences for the E265X truncating mutation between the 780 controls (1.9%), 1,204 sporadic prostate cancer cases (1.9%), or 350 familial/HPC prostate cancer cases (1.4%). Further, this group did not find significant differences between cases and controls for the R462Q variant. A meta-analysis summarized the data from ten case-control studies that contained data on the RNASEL variants E265X, R462Q and D541E. Only the D541E allele was associated with an increased risk of prostate cancer, although the magnitude of the effect was small. In summary, there is evidence both for and against rare and common RNASEL variants contributing to a proportion of familial prostate cancer cases, though larger studies are required to more carefully delineate both the clinical and biologic implications of germline RNASEL variants.
Prostate Cancer Predisposing Locus
A genome-wide scan using 49 high-risk prostate cancer families of German and French origin resulted in evidence of a prostate cancer predisposition locus on chromosome 1q42. This is believed to be a separate gene from the HPC1 locus at 1q24. Prostate cancer linkage to this locus, which has been designated PCAP, was described in a second set of European prostate cancer families  and families with evidence of linkage had an earlier average age at diagnosis (<65 years). PCAP linkage has not been observed in several studies of U.S. and international HPC families.[9,17,31,43,44,45,46,47,48,49,50]
Hereditary Prostate Cancer X
A prostate cancer susceptibility locus (designated HPCX) has been mapped to the X chromosome by using a set of high-risk prostate cancer families from the United States, Finland, and Sweden. In this initial report, linkage to a hypothesized gene located at Xq27-28 was predicted to account for 16% of prostate cancer among the 360 families that were analyzed. Analytic epidemiology studies have shown a higher relative risk (RR) of prostate cancer among men with an affected brother versus men with an affected father, a finding that supports the possibility of a prostate cancer susceptibility locus on the X chromosome; however, this pattern is also consistent with an autosomal recessive mode of inheritance or environmental factors. Follow-up HPCX linkage studies have shown some evidence in support of the existence of this locus,[46,53,54,55] and an ICPCG meta-analysis is in process. Using linkage disequilibrium analysis, a specific haplotype in the Xq27-28 region of HPCX was found to be significantly associated with X-linked prostate cancer in Finnish families. This finding was confirmed in a case control training set (292 cases and controls) and replicated in independent test subjects (215 cases and controls). The Xq27 haplotype extended from rs5907859 to rs1493189, and was associated with prostate cancer (OR = 3.41; 95% CI, 1.04–11.17; P = 0.034).
Many cancer susceptibility genes increase the risk for more than one type of malignancy. For example, BRCA1 mutations increase a woman's chance of developing both breast and ovarian cancer. In this regard, a set of prostate cancer families who have one or more cases of primary brain cancer was identified. In this set of 12 families, prostate cancer linkage to 1p36 markers was observed. This hypothetical gene locus has been named CAPB. Loss of heterozygosity (LOH) of this same genetic region was previously observed in sporadic brain cancers, suggesting that there is a tumor suppressor gene in this genomic interval. Other groups have not consistently confirmed prostate cancer linkage to CAPB in families with both brain and prostate cancers.[44,59] Further, there is evidence for linkage to 1p36 in one study of 207 prostate cancer families, considering as affected only those individuals with prostate cancer. This was particularly evident in families with early-onset disease in which the prostate cancer was diagnosed before age 59 years. This raises the possibility that CAPB mutations may contribute to prostate cancer in a site-specific manner.
The ELAC2/HPC2 prostate cancer predisposition gene on chromosome 17p was cloned after a genome-wide scan of high-risk families from Utah (Table 3). Two segregating germline mutations were identified among these multiplex prostate cancer families. Neither linkage evidence to 17p11 markers nor rare ELAC2/HPC2 variants were found in other sets of multiplex families. The ELAC2/HPC2 gene from 300 men from 150 prostate cancer families (with three or more cases of prostate cancer) was sequenced and identified only one stop codon and five additional missense mutations.
Two common variants in ELAC2/HPC2 have been extensively studied for their potential contribution to prostate cancer susceptibility. In a clinic-based study of 350 prostate cancer cases and 266 age-matched and race-matched controls, it was reported that men who carry both of two common polymorphisms in the ELAC2/HPC2 gene experience a modest increase in risk of prostate cancer (OR = 2.4; 95% CI, 1.1–5.3). Many additional studies have been reported, six of which have been pooled in a meta-analysis. The authors suggest that the use of unscreened controls in case-control studies results in the inclusion of a significant number of men with prostate cancer cases among subjects who are classified as controls. This misclassification error will bias association studies toward the null. In the ELAC2/HPC2 meta-analysis, if exclusion of data from association studies in which prostate cancer screening was performed in controls resulted in a positive association between the Thr541 substitution and prostate cancer risk (OR = 1.8; 95% CI, 1.2–2.7; P = .0029), then to the extent that misclassification bias is operating in this series, the reported OR may underestimate the strength of the observed association. Studies using population-based sampling might be expected to clarify the potential role of common ELAC2/HPC2 polymorphisms in prostate cancer. An Australian study found no significant association between ELAC2/HPC2 and prostate cancer. Furthermore, these authors pooled their new data with those from seven published studies; their meta-analysis strengthened the conclusion that no association exists.
Evidence for yet another prostate cancer susceptibility locus on chromosome 20, which has been termed HPC20, has been reported.[46,66] In stratified analyses, the group of patients with the strongest evidence of linkage to this locus were the families with fewer than five family members affected with prostate cancer, a later average age at diagnosis, and no male-to-male transmission, a pattern distinctly different from that reported for HPC1. Some evidence of prostate cancer linkage to HPC20 has been observed in two independent sets of families,[67,68] though the candidate genomic interval remains large; however, a combined linkage analysis of 1,234 pedigrees performed by the ICPCG failed to replicate linkage of hereditary prostate cancer to 20q13 markers. In this report, the original 158 Mayo families that were used to identify HPC20 had a maximum heterogeneity LOD score under a recessive model of 2.78 whereas the remaining 1,076 families has a maximum heterogeneity LOD score of 0.06 using the same model. These data suggest that if HPC20 truly exists, it may only account for a small fraction of all hereditary prostate cancers.
Chromosome 8p is commonly deleted in prostate cancer; consequently, many groups have focused on using deletion mapping in an attempt to localize one or more tumor suppressor genes in this region. Several genome-wide scans have provided modest evidence of prostate cancer linkage to markers that map to 8p.[31,47,70] Evidence has been reported that both rare and common variants in the macrophage scavenger receptor 1 gene (MSR1) at 8p22 are associated with prostate cancer susceptibility (Table 3).[71,72] Case-control studies examining an association between these alleles and prostate cancer, however, did not show significant findings, including a meta-analysis.[73,74,75,76] Germline variants of the LZTS1 gene, also at 8p22, have been reported to be associated with sporadic prostate cancer.
A combined analysis of somatic deletions of chromosome 8p in prostate cancer tumor tissue and fine-mapping linkage in multiple-case families has identified two additional regions (8p23.1 and 8p21.3) that are associated with prostate cancer risk.
A linkage peak at chromosome 8q24 was reported in 323 Icelandic prostate cancer families with a peak LOD score of 2.11. Detailed genotyping of this region revealed an association in three case-control populations in Sweden, Iceland, and the United States with allele-8 at marker DG8S737. The population attributable risk for prostate cancer from this allele was 8%. The results were replicated in an African American case-control population, in which the population attributable risk was 16%. Support for the existence of a prostate cancer susceptibility gene at 8q24, specifically in African American men, was also observed using admixture mapping.
A series of studies confirming the association between prostate cancer risk and single nucleotide polymorphism (SNP) rs1447295 has been published.[81,82,83,84,85,86,87] Three additional studies evaluating the 8q24 locus have identified a second SNP, rs6983267, which is close to but distinct from rs1447295.[84,88,89] Furthermore, a multiethnic analysis identified five new variants all within this same region, each of which appears to be independently associated with prostate cancer risk. A number of these variants are much more common than rs1447295, suggesting that the proportion of all prostate cancers that may be explained on the basis of genetic variation in this region could be quite large. The well-known differences in prostate cancer risk among diverse population groups also may be related to these findings.[89,90] For example, three SNPs from 8q24 that were previously shown to be associated with prostate cancer risk were studied in a low-risk, unscreened Asian-Indian population in northern India. SNPs rs1447295, rs16901979, and rs6983267 were evaluated in 153 cases and 227 age-matched controls for association with advanced prostate cancer. After adjusting for age, the OR was 1.77 (95% CI, 1.55–2.97) for carriers of the A allele of rs1447295 and was 1.85 (95% CI, 1.04–3.28) for carriers of the A allele of rs16901979. The OR for the combined effects of the A allele of rs1447295 with the A allele of rs16901979 was 2.61 (95% CI, 1.11–6.12). These results confirm the association of sequence variants at 8q24 with advanced prostate cancer in a unique population of Asian-Indian men.
A meta-analysis, including data from ten independent studies, has demonstrated a statistically significant association for four 8q24 variants in prostate cancer risk. These observations are also notable because they occur in a region without known protein-encoding genes, which makes it very difficult to know what the underlying biological mechanism of susceptibility is likely to be. This is likely a recurring situation with genome-wide association studies (GWAS) in which statistically convincing associations are detected, but the truly causal variant and biological mechanism will be difficult to determine, requiring biochemical and other functional studies. C-MYC is the closest cancer-related gene to the 8q candidate region. At least one study has demonstrated an association between a SNP in the first intron of c-MYC and prostate cancer, raising the possibility that the c-MYC gene is associated with the overall 8q association findings. These susceptibility alleles are generally associated with an OR of 2 or lower and are not immediately clinically relevant.
Refer to the Polymorphisms and Prostate Cancer Susceptibility section of this summary for more information on polygenic factors in 8q.
Chromosome 8q24 risk variants have also been characterized in families with HPC. Twelve 8q24 variants from Regions 1, 2, and 3 and one variant from the c-MYC gene were genotyped in 168 probands from HPC families: 1,404 prostate cancer patients from non-HPC families undergoing radical prostatectomy, and 560 control subjects undergoing prostate cancer screening at Johns Hopkins University. Risk alleles from five SNPs in Region 1 (rs1447295, rs4242382, rs7017300, rs10090154, and rs7837688) and alleles from two SNPs in Region 2 (rs6983561 and rs16901979) were significantly more frequent in HPC probands compared with controls. Genotype risk for HPC was also higher for these seven SNPs. Family-based transmission tests found that risk alleles of two SNPs in Region 2 were significantly over-transmitted to affected men in these HPC families. No evidence for linkage to 8q24 was found in these HPC families. Another report from the University of Michigan Prostate Cancer Genetics Project (UM-PCGP) evaluated five SNPs and one microsatellite marker found previously to be associated with prostate cancer in 403 non-Hispanic white families with discordant sibling pairs. Using a family-based association test, the minor allele of rs6983561 and the major allele of rs6983267 were found to be preferentially transmitted to affected men. Furthermore, rs6983561 was significantly associated with prostate cancer among men diagnosed before age 50 years and rs6983267 was significantly associated with clinically aggressive disease. These data provide further support for modification of familial prostate cancer risk by variants in 8q24, particularly variants from Region 2. There are more than three linkage disequilibrium blocks that have been demonstrated to contain loci that are independently associated with prostate cancer, emphasizing the complex structure of this region.[95,96].
Table 2 summarizes the proposed prostate cancer susceptibility loci identified in families with multiple prostate cancer–affected individuals. Conflicting evidence exists regarding the linkage to some of the loci listed above. Data are also limited on the proposed phenotype associated with each loci, and the strength of repeated studies is needed to firmly establish these associations. Evidence suggests that many of these prostate cancer loci account for disease in a small subset of families, which is consistent with the concept that prostate cancer exhibits locus heterogeneity.
Table 2. Proposed Prostate Cancer Susceptibility Loci
|Gene||Location||Candidate Gene||Clinical Testing||Proposed Phenotype||Comments|
|HPC1(OMIM)[20,21,22,23,24,25,26,27,28,29,30,31,32,35,36,37,38,39,40]||1q24–25||RNASEL||Not available||Younger age at prostate cancer diagnosis (<65 years)||Evidence of linkage is strongest in families with 5 or more affected persons, young age at diagnosis, and male-to-male transmission|
|Higher tumor grade (Gleason Score)|
|More advanced stage at diagnosis||RNASEL mutations have been identified in some 1q-linked families|
|PCAP(OMIM)[9,17,20,24,31,42,43,44,45,46,47,48,49,50]||1q42.2–43||None||Not available||Younger age at prostate cancer diagnosis (<65 years)||Evidence of linkage strongest in European families|
|HPCX(OMIM)[46,51,52,53,54,55]||Xq27–28||None||Not available||Unknown||May explain observation that an unaffected man with an affected brother has a higher risk than an unaffected man with an affected father|
|CAPB(OMIM)[44,58,59]||1p36||None||Not available||Younger age at prostate cancer diagnosis (<65 years)||Strongest linkage evidence was initially described in families with both prostate and brain cancer; follow-up studies indicate that this locus may be associated specifically with early-onset prostate cancer but not necessarily brain cancer|
|One or more cases of brain cancer|
|HPC20(OMIM)[46,66,67,68,69]||20q13||None||Not available||Later age at prostate cancer diagnosis||Linkage evidence strongest in families with late age at diagnosis, fewer affected family members, and no male-to-male transmission|
|No male-to-male transmission|
|8P[31,47,70,71,72,73,74,75,76,77,78]||8p21–23||MSR1||Not available||Unknown||In a genomic region commonly deleted in prostate cancer|
|8Q[79,80,81,82,83,84,88,89,93,94]||8q24||None||Not available||Unknown||Population attributable risk was higher in African American men than in men of European origin|
BRCA1 and BRCA2
Among male BRCA1 mutation carriers from hereditary breast ovarian cancer kindreds studied by the Breast Cancer Linkage Consortium (BCLC) family set, the risk of prostate cancer was not elevated overall (RR = 1.1; 95% CI, 0.8–1.5); however, the risk was modestly increased (RR = 1.8; 95% CI, 1.0–3.3) among men younger than 65 years.
In contrast, a similar study of male BRCA2 mutation carriers in hereditary breast ovarian cancer kindreds from the BCLC demonstrated that the risk of prostate cancer associated with BRCA2 mutations was increased overall (RR = 4.7; 95% CI, 3.5–6.2). The incidence was also markedly increased among men younger than 65 years at diagnosis (RR = 7.3; 95% CI, 4.7–11.5). Another report from the BCLC suggests that prostate cancer risk may be lower among men with a mutation in the central region of the BRCA2 gene, known as the ovarian cancer cluster region (RR = 0.5; 95% CI, 0.2–1.0).
Several small case series in Israel and in North America have analyzed the frequency of BRCA founder mutations among Ashkenazi men with prostate cancer.[101,102,103] Two specific BRCA1 mutations (185delAG and 5382insC) and one BRCA2 mutation (6174delT) are common in individuals of Ashkenazi (Eastern European) Jewish ancestry. Carrier frequencies for these mutations in the general Jewish population are 0.9% (95% CI, 0.7%–1.1%) for the 185delAG mutation, 0.3% (95% CI, 0.2%–0.4%) for the 5382insC mutation, and 1.3% (95% CI, 1.0%–1.5%) for the BRCA2 6174delT mutation.[104,105,106,107] (Refer to the Major Genes section of the PDQ summary on Genetics of Breast and Ovarian Cancer for more information on the BRCA1 and BRCA2 genes.) In these studies, the point estimates of risk were commonly greater than 1, but only a few have been statistically significant. Many of these studies were not sufficiently powered to rule out a lower, but clinically significant, risk of prostate cancer in carriers of Ashkenazi BRCA founder mutations.
In a study of more than 5,000 American Ashkenazi Jewish volunteers from the Washington D.C. area (the Washington Ashkenazi Study [WAS]), a kin-cohort analytic approach was used to estimate the cumulative risk of prostate cancer among men who carried one of the BRCA Ashkenazi founder mutations. The cumulative risk to age 70 years was estimated to be 16% (95% CI, 4%–30%) compared with 3.8% among noncarriers (95% CI, 3.3%–4.4%). This fourfold increase in prostate cancer risk was equal (in absolute terms) to the cumulative risk of ovarian cancer among female mutation carriers at the same age (16% by the age of 70 years; 95% CI, 6%–28%). The risk of prostate cancer in male mutation carriers in the WAS cohort was elevated by age 50 years, was statistically significantly elevated by age 67 years, and increased thereafter with age, suggesting both an overall excess in prostate cancer risk and an earlier age at diagnosis among carriers of Ashkenazi founder mutations. Prostate cancer risk differed depending on the gene, with BRCA1 mutations associated with increasing risk after age 55 to 60 years, reaching 25% by age 70 years and 41% by age 80 years. In contrast, prostate cancer risk associated with the BRCA2 mutation began to rise at later ages, reaching 5% by age 70 years and 36% by age 80 years (numeric values were provided by the author [written communication, April 2005]).
Two studies using similar methods examined the prevalence of Ashkenazi founder mutations among Jewish men with prostate cancer and found an overall positive association between founder mutation status and prostate cancer risk. The first study  analyzed 979 consecutive Ashkenazi men with prostate cancer diagnosed in a large region of Israel, and compared the prevalence of founder mutations with age-matched controls from two different sources, the WAS and the Molecular Epidemiology of Colorectal Cancer (MECC) study from Israel. Overall, there was a twofold, statistically significant increase in the risk of prostate cancer among all carriers of founder mutations (OR = 2.1; 95% CI, 1.2–3.6). The magnitude of this risk was similar for BRCA1 and BRCA2 founder mutations, but only the BRCA2 association was statistically significant, when considered separately. This study did not find that mutation carriers developed prostate cancer at an earlier-than-usual age. Further, there was no evidence of unique or specific histopathology findings within the mutation-associated prostate cancers.
The second study  tested genomic DNA from 251 Ashkenazi men diagnosed with prostate cancer at their institution for the three common BRCA1/2 founder mutations. Using the control data from the WAS study described above, and after adjusting for age, all founder mutation carriers had a significantly increased risk of prostate cancer (OR = 3.4; 95% CI, 1.6–7.1). When evaluating BRCA1 versus BRCA2 founder mutations separately, no significantly increased risk of prostate cancer was detected for BRCA1 mutation carriers, while the risk among BRCA2 mutation carriers was increased substantially (OR = 4.8; 95% CI, 1.9–12.2).
These two studies support the hypothesis that prostate cancer occurs excessively among carriers of Ashkenazi Jewish founder mutations, and both suggest that the risk may be greater among men with the BRCA2 founder mutation (6174delT) than those with one of the BRCA1 founder mutations (185delAG; 5382insC). The magnitude of the BRCA2-associated risks differ somewhat, undoubtedly because of interstudy differences related to participant ascertainment, calendar time differences in diagnosis, and analytic methods.
Two hundred sixty-three men with prostate cancer diagnosed in the United Kingdom (U.K.) before the age of 56 years underwent testing for BRCA2 mutations. Screening of all coding regions resulted in the identification of six men (2.3%) with protein-truncating BRCA2 mutations, as well as an additional 22 men harboring variants of undetermined significance. Three of the men with deleterious mutations had no family history of prostate, breast, or ovarian cancer. Using estimates of the frequency of BRCA2 mutations in the general U.K. population of 0.14% and 0.12%, the investigators estimated a 23-fold RR of early-onset prostate cancer attributable to BRCA2 mutations (95% CI, 9–57). In a similar study conducted in a U.S. population, 290 men (11% African American and 87% Caucasian) diagnosed with prostate cancer prior to age 55 years, unselected for family history, were screened for BRCA2 mutations. Two protein-truncating BRCA2 mutations were identified for a prevalence of 0.69% (95% CI, 0.08–2.49%). Both mutations were found in Caucasian cases for a prevalence in Caucasians of 0.78% (95% CI, 0.09–2.81%) and a 7.8 (95% CI, 1.8–9.4) RR of prostate cancer in Caucasian BRCA2 mutation carriers. Of the two individuals with a protein truncating mutation, neither reported a family history of breast or ovarian cancer. This study confirms that on rare occasions germline mutations in BRCA2 account for some cases of early-onset prostate cancer, although this is estimated to be less than 1% of early-onset prostate cancers in the U.S.
A founder mutation in BRCA2 (999del5 in exon 9), which was originally described in male and female breast cancer families in Iceland, has been reported to be associated with aggressive prostate cancer in multiple small studies.[112,113,114,115,116,117] A recent population-based case-control study between BRCA2 999del5 mutation carriers and noncarriers (all of whom had a prostate cancer diagnosis) from the Icelandic Cancer Registry was conducted. Five hundred and twenty-seven out of 596 prostate cancer patients from Iceland with prostate tissues available for pathology review had genetic analysis performed. Thirty patients carrying this BRCA2 mutation were identified and matched to 59 noncarriers by year of diagnosis and year of birth. The results showed that mutation carriers had lower mean age of prostate cancer diagnosis, advanced tumor stage, higher tumor grade, and shorter median survival than noncarriers. Carrying the BRCA2 999del5 mutation was associated with a higher risk of death from prostate cancer (hazard ratio [HR] = 3.42; 95% CI, 2.12–5.51) which remained after adjustment for stage and grade (HR = 2.35; 95% CI, 1.08–5.11). These investigators concluded that the Icelandic BRCA2 999del5 founder mutation was associated with aggressive prostate cancer. Their observations differ from similar analyses of BRCA-related prostate cancer in other population groups and may be specific for the Icelandic founder mutation.
Genomic DNA of 266 subjects from 194 HPC families was screened for BRCA2 mutations using sequence analysis focusing on exonic and preserved regulatory regions. Although a number (n = 31) of nonsynonymous variations were identified, no truncating or deleterious mutations were detected. These investigators concluded that BRCA2 mutations did not significantly contribute to hereditary prostate cancer. A genome-wide scan for HPC using 175 families from the University of Michigan Prostate Cancer Genetics Project (UM-PCGP) found evidence for linkage to chromosome 17q markers. The maximum LOD score in all families was 2.36, and the LOD score increased to 3.27 when only those families with four or more confirmed affected men were analyzed. The linkage peak was centered over the BRCA1 gene. In follow-up, these investigators screened the entire BRCA1 gene for mutations using DNA from one individual from each of 93 pedigrees with evidence of prostate cancer linkage to 17q markers. Sixty-five of the individuals screened had wild-type BRCA1 sequence, and only one individual from a family with prostate and ovarian cancer was found to have a truncating mutation (3829delT). The remainder of the individuals harbored one or more germline BRCA1 variants, including 15 missense variants of uncertain clinical significance. The conclusion from these two reports is that there is evidence for a prostate cancer susceptibility gene on chromosome 17q near BRCA1; however, large deleterious inactivating mutations in BRCA1 are not likely to be associated with prostate cancer risk in chromosome 17-linked families.
In another study from the UM-PCGP, common genetic variation in BRCA1 was examined. Conditional logistic regression analysis and family-based association tests were performed in 323 familial and early-onset families, which included 817 men with and without prostate cancer to investigate the association of SNPs tagging common haplotype variation in a 200-kb region surrounding and including BRCA1. Three SNPs in BRCA1 (rs1799950, rs3737559, and rs799923) were found to be associated with prostate cancer. The strongest association was observed for SNP rs1799950 (OR = 2.25; 95% CI, 1.21–4.20), which leads to a glutamine-to-arginine substitution at codon 356 (Gln356Arg) of exon 11 of BRCA1. Furthermore, SNP rs1799950 was found to contribute to the linkage signal on chromosome 17q21 originally reported by the UM-PCGP. These findings support further investigation of BRCA1 variants in prostate cancer risk.
In an effort to clarify the relationship between BRCA1/BRCA2 and prostate cancer risk, 215 BRCA1-positive and 188 BRCA2-positive families were studied. One hundred fifty-eight of these men were diagnosed with prostate cancer, eight of whom were known to carry their family's BRCA1 mutation, and 20 who were known to carry a BRCA2 mutation. Archival pathology material (paraffin blocks) was retrievable from four men with a BRCA1 mutation and 14 men with a BRCA2 mutation. LOH was observed at the BRCA2 locus in 10 of 14 BRCA2-related prostate cancers versus 0 of 4 BRCA1-related prostate cancers (P = 0.02). BRCA2 mutation carriers were estimated to have a 3.5-fold increased prostate cancer risk, while BRCA1 mutation carriers did not appear to be at increased risk. These observations are consistent with the hypothesis that BRCA2, but not BRCA1, is a tumor suppressor gene related to prostate cancer risk. The absence of mutation information on the 130 unstudied cases limits the value of this observation. A recent review of the relationship between germline mutations in BRCA2 and prostate cancer risk, supports the view that this gene confers a significant increase in risk among male members of hereditary breast and ovarian cancer families, but that it likely plays only a small role, if any, in site-specific, multiple-case prostate cancer families.
Three Polish BRCA1 founder mutations (C16G, 4153delA, 5382insC) were studied in 1,793 Polish prostate cancer cases and 4,570 controls. Overall, the prevalence of the three mutations combined was identical in cases and controls. However, most common mutation, 5382insC, occurred in 0.06% of cases versus 0.37% of controls, suggesting that this specific variant is not likely to be associated with increased prostate cancer risk. Furthermore, the presence of either one of the other two mutations was associated with a 3.6-fold increase in prostate cancer risk (P = 0.045), and an even greater risk (OR = 12; P = 0.0004) of familial prostate cancer. These data suggest that prostate cancer risk in BRCA1 mutation carriers varies with the location of the mutation, i.e., there is a correlation between genotype and phenotype. This observation might explain some of the inconsistencies encountered in prior studies of this association, since populations may have varied relative to the proportion of persons with specific pathogenic BRCA1 mutations.
Analysis of prostate cancer cases in families with known BRCA1 or BRCA2 mutations were examined for survival. The study suggests that BRCA2 mutation carriers have a poorer survival compared with BRCA1 mutation carriers. This potentially important observation requires confirmation.
The relationship between the Ashkenazi Jewish (AJ) founder mutations in BRCA1 and BRCA2 was evaluated in 979 prostate cancer cases and 1,251 controls in this population. When analyzed by individual mutation, no statistically significant increases in prostate cancer risk were observed, although a nonsignificant increase in risk related to BRCA2-6174delT was described (OR = 1.92; 95% CI 0.91–4.07). A significant increase in the risk of prostate cancer was observed in men with high-grade (Gleason score 7 or greater) prostate cancers with both BRCA2-6174delT (OR = 3.18; 95% CI, 1.37–7.34) and BRCA1-185delAG (OR = 3.54; 955 CI, 1.22–10.31) mutations. These findings suggest that the previously reported relationship between the AJ founder mutations and prostate cancer risk may be accounted for by high-grade prostate cancers. These observations require confirmation in additional studies since the design of the current report (nationwide volunteers recruited through the mail) leaves open the possibility of ascertainment bias.
Thus, the literature suggests that there may be a modest increase in prostate cancer risk among men with one of the Ashkenazi founder mutations, and a more substantial increase in risk among BRCA2 carriers in general; the risk is unclear among BRCA1 mutation carriers. These observations may comprise one of many factors that a man contemplating BRCA mutation testing might consider. Uncertainties regarding screening and management of men at increased risk of prostate cancer make it difficult to encourage BRCA mutation testing solely for prostate cancer risk management. (Refer to the Mutations in BRCA1 and BRCA2 section of the PDQ summary on Genetics of Breast and Ovarian Cancer and the Screening section of this summary for more information about testing for BRCA1 and BRCA2.)
The tumor suppressor gene Kruppel-like factor 6 (KLF6), located on chromosome 10p15, is a zinc finger transcription factor potentially associated with prostate cancer risk. Somatic mutations and allelic loss of KLF6 have been found in tumors of several primary neoplasms, including prostate cancer. A germline mutation in KLF6 (IVS1-27G>A) appears to have a novel mechanism of gene inactivation: generation of alternatively spliced products that antagonize wild-type gene function. However, data are inconsistent regarding the association of germline mutations in KLF6 and hereditary prostate cancer. A Finnish study of 69 prostate cancer families did not identify an association between KLF6 mutations and prostate cancer susceptibility. The germline KLF6 SNP described above, IVS1-27G>A, was found to increase the RR of prostate cancer in a U.S. study of 3,411 men (RR = 1.61, P = .01; 95% CI, 1.20–2.16). However, the prostate cancer risk associated with the IVS1-27G>A SNP was not detected in a study of 300 Jewish prostate cancer families. In fact, the A allele, which was previously shown to be more common in U.S. men with prostate cancer and associated with the creation of splice variants, was significantly less common among cases than among controls in this Israeli study (49/804 alleles in cases compared with 55/600 control alleles; P = .030).
The alpha methylacyl-CoA racemase (AMACR) gene, located at 5p13.3, encodes a protein that is localized to peroxisomes and mitochondria and plays an important role in the metabolism of branch-chained fatty acids. The protein has been shown to be overexpressed in many cancers including prostate cancer. AMACR resequencing experiments using DNA from probands in HPC families were conducted. From the 17 sequence variants identified, 11 SNPs were selected for genotyping in 159 HPC probands, 245 sporadic prostate cancer cases and 211 controls. Several variants (including M9V, G1157D, S291L, and K277E) were shown to be associated with HPC (but not sporadic prostate cancer). A haplotype-tagging strategy was used to test for association between genetic variation in AMACR and prostate cancer in a set of siblings discordant for prostate cancer who are participating in a research study focused on early-onset and/or HPC. The strongest evidence for association was for SNP rs3195676 (M9V) with an OR of 0.58 (95% CI, 0.38–0.90, P = 0.01 for a recessive model). The reported magnitude and direction of the association observed for this SNP was similar between this study and previously mentioned AMACR resequencing experiments. A nested case-control study was conducted using samples from the screening arm of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening trial to test for potential association between 7 AMACR SNPs and prostate cancer including M9V. No association was detected between any of the SNPs and prostate cancer. Note that the prostate cancer cases in the PLCO study are all older than 55 years and not specifically enriched for family history. Risk for prostate cancer was reduced, however, in men who reported using ibuprofen who also had specific alleles and 4 SNPs (M9V, D175G, S201L and K77E) or a specific six-SNP haplotype. Ibuprofen mediates its anti-inflammatory effect through COX2 inhibition; AMACR contributes to the conversion of the COX-inactive to the COX-active form of ibuprofen. This observation suggests that these AMACR SNPs may alter enzyme function although experiments have not been conducted to directly test this hypothesis.
Other Potential Prostate Cancer Genes
Individuals who were heterozygous for one of the Nijmegen Breakage syndrome (NBS) founder mutations identified in Poland may be at increased risk of prostate cancer. NBS is a rare autosomal recessive cancer susceptibility disorder of childhood that is characterized by growth retardation, facial dysmorphism, immunodeficiency, and a predisposition to lymphoma and leukemia in patients with germline biallelic (e.g., homozygous) mutations. NBS1, located on chromosome 8q, has an important role in DNA repair and is part of the ataxia telangiectasia pathway. Recent observations have suggested that there may be an increased risk of cancer among heterozygous carriers of mutations in a number of genes involved in response to DNA damage, such as xeroderma pigmentosum  and ataxia telangiectasia.[136,137] Polish investigators analyzed the prevalence of an NBS1 founder mutation in a sample of 56 men with familial prostate cancer, 305 men with sporadic cancer, and control subjects who included men, women, and newborns. Cases with a positive family history were 16 times more likely to be mutation carriers than were controls (P<.0001). LOH was commonly observed in mutation-associated prostate cancers, with preferential loss of the wild-type allele. A collaborative report from five groups participating in the ICPCG demonstrated a carrier frequency of 0.22% (2 of 909) for probands with familial prostate cancer and 0.25% (3 of 1,218) for men with sporadic cancer for the founder 657del5 mutation. Although this mutation was not detected in any of the 293 unaffected family members, the low frequency of the founder mutation suggests that NBS1 mutations do not contribute to a significant proportion of prostate cancer cases.
In the first report of possible germline CHEK2 variants in men with prostate cancer, mutations were identified in 4.8% of 578 prostate cancer patients and in none of 423 unaffected men. Nine of 149 multiplex prostate cancer families were also found to have germline CHEK2 mutations. The I157T substitution was detected in equal numbers of cases and controls and thus was felt to likely represent a polymorphism. Functional studies of additional identified variants revealed substantial reductions in CHEK2 protein levels and/or other functional changes that suggest CHEK2 mutations contribute to prostate carcinogenesis.[139,140] Subsequently, Polish investigators sequenced the CHEK2 gene in 140 patients with prostate cancer, and then analyzed the three detected variants in a larger series of prostate cancer cases and controls. CHEK2 truncating mutations were identified in 9 of 1,921 controls (0.5%) and in 11 of 690 (1.6%) unselected patients with prostate cancer (OR = 3.4; P = .004). These same mutations were also found in 4 of 98 familial prostate cases (OR = 9.0; P = .0002). The I157T missense variant was also more frequent in men with prostate cancer (7.8%) than in controls (4.8%) (OR = 1.7; P = .03), and was identified in 16% of men with familial prostate cancer (OR = 3.8; P = .00002). LOH was not observed in any of the five men with truncating CHEK2 mutations. A follow-up to this study has been reported from Poland with 1,864 prostate cancer patients and 5,496 controls. All three founder mutations as well as a large germline deletion of exons 9 and 10 (5395-bp deletion) were genotyped. The truncating mutation 1100delC was identified in 14 of 1,864 (0.8%) unselected prostate cancer cases and 3 of 249 (1.2%) familial cases (OR = 3.5; P = .002 and OR = 5.6; P = .02, respectively). A significant association with another truncating mutation (IVS2+1G?A) was identified in 5 of 249 (2.0%) familial cases that had the mutation (OR = 5.1; P = .002). The missense mutation I157T was detected in 142 of 1,864 (7.6%) unselected prostate cancer cases and in 30 of 249 (12%) familial cases (OR = 1.6; P<.001 and OR = 2.7; P<.001, respectively). The large deletion in exons 9 and 10 accounted for 4 of 249 (1.6%) familial cases (OR = 3.7; P = .03). Overall, it appears that there are at least four founder mutations in the CHEK2 gene, which account for an estimated 7% of patients with prostate cancer in the Polish population. The most common missense mutation is I157T, and the most common truncating mutation is 5395-bp deletion. These reports suggest that truncating and missense mutations in CHEK2 may play a role in prostate cancer susceptibility. However, a recent molecular analysis designed specifically to assess the role of seven different CHEK2 coding variants (including 1100delC) in Ashkenazi Jewish men with prostate cancer, suggested that germline mutations in this gene have a minor role, if any role at all, in modifying the risk of prostate cancer in Ashkenazi Jewish men. This conclusion is limited by the relatively small number of individuals in whom CHEK2 sequencing was performed.
Table 3 summarizes the candidate genes for prostate cancer susceptibility, their chromosomal location, and availability of clinical testing.
Table 3. Candidate Genes for Prostate Cancer Susceptibility
|Gene||Location||Clinical Testing||Proposed Phenotype||Comments|
|BRCA1(OMIM)[97,101,102,103,104,105,106,107,120,144,145]||17q21||Available||Younger age at prostate cancer diagnosis (<65 years); earlier age at diagnosis among carriers of Ashkenazi founder mutations.||There is some evidence that men with a BRCA1 mutation may develop prostate cancer at an earlier age.|
|BRCA2(OMIM)[99,100,101,102,103,105,106,107,108,109,110,145]||13q12-13||Available||Younger age at prostate cancer diagnosis (<65 years); earlier age at diagnosis among carriers of Ashkenazi founder mutations.||Prostate cancer risk may be lower among men with a mutation in the central region of the BRCA2 gene.|
|RNASEL(OMIM)[20,21,22,23,24,25,26,27,28,29,30,31,32,35,36,37,38,39,40,146]||1q24-25||Not available||Unknown||Rare and common RNASEL variants may contribute to a proportion of familial prostate cancer cases.|
|RNASEL is a candidate gene for HPC1 (Table 2).|
|ELAC2/HPC2(OMIM)[60,61,62,63,64,65,146]||17p||Not available||Unknown||Infrequent deleterious mutations identified in HPC families in follow-up reports.|
|MSR1(OMIM)[71,72,76,130,146]||8p22||Not available||Unknown||In a genomic region commonly deleted in prostate cancer.|
|NBS1(OMIM)[134,138]||8q21||Available||Increased prostate cancer risk in heterozygotes.||Infrequent NBS1 mutations, including founder 657del5 variant, in follow-up study.|
|CHEK2(OMIM)[139,141,142]||22q12.1||Available||Unknown||Value of clinical testing for mutations in CHEK2 for prostate cancer risk is not established.|
|KLF6(OMIM)[127,128,129,130,147]||10p15||Not available||Younger age at prostate cancer diagnosis (<65 years).|
To summarize, studies to date have mapped site-specific prostate cancer susceptibility loci to chromosomes 1q24–25 (HPC1), 1q42.2–43 (PCAP), 1p36 (CAPB), Xq27–2 (HPCX), 20q13 (HPC20), 17p (ELAC2/HPC2), and 8p. Other studies have suggested that prostate cancer may be part of the cancer spectrum of syndromes that include a more diverse set of malignancies, such as seems to be the case for BRCA2 and, perhaps, BRCA1. Both linkage and candidate gene studies have been complicated by the late-onset nature of the disease and the high background rate of prostate cancer in the general population. In addition, there is likely to be real, extensive locus heterogeneity for HPC, as suggested by both segregation and linkage studies. In this respect, HPC resembles a number of the other major adult-onset hereditary cancer syndromes, in which more than one gene can produce the same or very similar clinical phenotype (e.g., hereditary breast/ovarian cancer, Lynch syndrome, hereditary melanoma, and hereditary renal cancer).
Linkage studies may be used to evaluate the possibility that an HPC gene might exist in a particular family, but this analytic approach is currently being done only in the research setting. Until the specific genes and mutations involved are identified, it is difficult to establish the analytical validity of this approach. Without a validated laboratory test, clinical validity and clinical utility cannot be measured. At present, clinical germline mutation testing for HPC susceptibility is not available.
Other Regions Identified by Linkage Studies
Genome-wide linkage studies of families with prostate cancer have identified several other loci that may harbor prostate cancer susceptibility genes, emphasizing the underlying complexity and genetic heterogeneity of this cancer. The chromosomal regions with modest-to-strong statistical significance (LOD score of 2 or more) include the following chromosomes:
- 2q21 
- 2q23 
- 3p14 (ECOG-01Y97) [149,150,151]
- 3p24-26 [12,49,152,153]
- 4q21 
- 4q35 
- 5p13q12 
- 5q11-12 [12,50]
- 5q35 [12,156]
- 6p22.3 [47,157]
- 7q21 
- 7q32 [17,47,156,158]
- 8q11 
- 8q13 [12,159]
- 9q34 [17,31]
- 11p11.2-q12.2 
- 11q22 [12,161]
- 13q14 
- 15q11 [12,154]
- 15q12 
- 15q13-q14 
- 16p13 
- 16q23 [17,162]
- 17p12 
- 17q21-22 [12,48,154,163,164,165,166,167]
- 17q25 
- 18q21 
- 19q [16,19,156]
- 19p13.3 
- 22q12.3 [12,13,161,168,169,170]
- Xq12 
Combined analyses have helped to prioritize candidate regions for further study.
The African American Hereditary Prostate Cancer study conducted a genome-wide linkage study on 77 families with four or more affected men. Multipoint heterogeneity LOD (hLOD) scores greater than or equal to 1.3 and less than 2.0 were observed using markers that map to 11q22, 17p11, and Xq21. Analysis of the 16 families with more than six men with prostate cancer provided evidence for two additional loci: 2p21 (multipoint hLOD score of 1.08) and 22q12 (multipoint hLOD score of 0.91).[12,161]
A study describes a linkage analysis targeting families with clinically aggressive prostate cancer (defined by Gleason grade =7, PSA =20 ng/mL, and cancer stage). One hundred twenty-three families with two or more affected family members with aggressive prostate cancer were studied. Suggestive linkage was found at chromosome 22q11 (hLOD score of 2.18) and 22q12.3-q13.1 (hLOD score of 1.90). These findings suggest that using a clinically defined phenotype may facilitate finding prostate cancer susceptibility genes. A fine mapping study of 14 extended high-risk prostate cancer families has subsequently narrowed the genomic region of interest to an 880-kb region at 22q12.3. No candidate genes have been identified. An analysis of high risk pedigrees from Utah provides an overview of this strategy.
A genome-wide linkage study was conducted to identify a susceptibility locus that may account for both prostate cancer and kidney cancer in families. Analysis of 15 families with evidence of HPC as well as one or more cases of kidney cancer (pathologically confirmed) in a man with prostate cancer or in a first-degree relative of a case revealed suggestive linkage with markers that mapped to an 8 cM region of chromosome 11p11.2-q12.2. This observation awaits confirmation.
Genome-wide Association Studies
Genome-wide searches are showing great promise in identifying common, low-penetrance susceptibility alleles for many complex diseases, including prostate cancer. In contrast to assessing candidate genes and/or alleles, GWAS involve comparing a very large set of genetic variants spread throughout the genome. This approach can be contrasted with linkage studies in which co-segregation of a genetic trait and genetic variants within multiplex families is assessed and with candidate gene studies which focus on one or more known genes that are biologically implicated in the disease. The current paradigm uses sets of 100,000 to 1,000,000 SNPs that are chosen to capture a large portion of common variation within the genome based on the HapMap project.[173,174] The SNPs that are studied in most GWAS are common, with minor allele frequencies, greater than 1% to 5%, in the specific population under study (e.g., men of European ancestry).
By comparing allele frequencies between a large number of cases and controls, typically 1,000 or more of each, and validating promising signals in replication sets of subjects, very robust statistical signals of association have been obtained.[175,176,177] The strong correlation between many SNPs that are physically close to each other on the chromosome (linkage disequilibrium) allows one to "scan" the genome for susceptibility alleles even if the biologically relevant variant is not within the tested set of SNPs. While this between–SNP correlation allows one to interrogate the majority of the genome without having to assay every SNP, when a validated association is obtained, it is not usually obvious which of the many correlated variants is the causal one. Another issue regarding GWAS is that studies that are focused on admixed groups need to be wary of the potential for population stratification which can lead to false-positive association signals when the frequency of genetic variants and the frequency of the disease under study are both increased in a population, such as prostate cancer in African American men. Finally, allelic heterogeneity (where multiple variants in the same gene can increase or decrease the risk for prostate cancer) can impact the results of GWAS. Additional detail can be found elsewhere.
A two-stage GWAS was conducted for prostate cancer susceptibility. In the first stage, 527,869 SNPs were studied using 1,172 cases and 1,157 controls of European ancestry from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening trial. Approximately 5% of the SNPs (26,598), those with the most evidence for disease association, were taken to the second stage and tested in a set of 3,941 cases and 3,964 controls of European origin derived from four additional study populations. Combined joint analysis using the initial scan results with those from the four follow up studies confirmed the association between prostate cancer and the hepatocyte nuclear factor-1-beta (HNF1B) gene, a finding that has been previously reported.[89,164] A fine-mapping study of this genomic region revealed a second strongly associated SNP (rs11649743) which was independent from the effect of the previously reported SNP. Several additional loci approximated or achieved the genome-wide level of statistical significance (p < 10-7).[89,164] These loci included rs10896449 in the promoter of MSMB (10q11.2), rs10896449 at 11q13, rs4962416 in the fifth intron of CTBP2 (chromosome 10) and rs10486567 in the second intron of JAZF1 (7p15).
A GWAS conducted in the United Kingdom and Australia compared 1,854 prostate cancer cases with 1,894 controls. This study used cases that were diagnosed based on clinical symptoms, rather than PSA screening, and was enriched for genetic susceptibility through selection of men with early-onset prostate cancer (diagnosis before age 60 years) and/or family history. The DNA samples were typed using 569,243 SNPs, and 53 SNPs were found to be significantly associated with prostate cancer at the p < 10-6 level. Twenty of the 53 SNPs were at 8q24 and six were at 17q12; both regions have been implicated in prior studies of prostate cancer risk. There are data to suggest that risk variants at 8q24 and 17q may have a cumulative effect on age at diagnosis of prostate cancer, i.e., decreasing age at diagnosis with increasing number of risk variants. Using an alternative design (family-based association) the 17q12 finding has been corroborated particularly in hereditary prostate cancer and early-onset prostate cancer. A similar association has been found in an African American population. Eleven SNPs from the previously described study  were subsequently studied in a second-stage sample comprising of 3,268 cases and 3,366 controls. Seven SNPs were independently associated with prostate cancer in this analysis including SNPs on chromosomes 3, 6, 7, 10, 11, 19 and X. Of note, the MSMB gene at 10q11.2 was implicated in both the PLCO and U.K. studies. A fine-mapping study of SNPs in MSMB and the region surrounding MSMB on 10q11.2 identified and confirmed the association of SNP rs10993994 with prostate cancer risk in 2,899 cases and 1,722 controls in Sweden (OR = 1.15; 95% CI, 1.06–1.25, P = 1.5x10-3). In addition, a functional analysis of the risk allele of rs10993994 (which is located upstream from the transcription start site of MSMB) in the LnCaP prostate cancer cell line found the risk allele resulted in an 87% reduction in promoter activity compared with the nonrisk allele. The association with the rs10993994 risk allele has also been observed in a series of familial prostate cancer cases. A confirmatory study using data from the prostate cancer association group to investigate cancer associated alterations in the genome (PRACTICAL) consortium, which included 7,370 cases and 5,742 controls, reported increasing ORs for six of the SNPs previously identified in the United Kingdom/Australia study. As the number of risk alleles increased the OR of prostate cancer increased (OR = 1.0 to OR = 3.5 for 0 vs. six risk alleles, respectively).
To identify additional variants associated with prostate cancer, two candidate SNPs were selected from a prior GWAS  based on either being X-linked (rs5945572; Xp11.22) or associated with aggressive prostate cancer (Gleason =7 and/or =T3 and/or node positive and/or metastasis) (rs2710646 2p15). Using the Utah CEPH HapMap data, several SNPs not represented in the prior study were selected for genotyping in 1,500 Icelandic cases and 800 Icelandic controls based on whether there was correlation with either of the candidate variants, rs5945572 or rs2710646. None of the newly selected SNPs were found to be more strongly associated with prostate cancer than the two candidate variants. The original two SNPs were then analyzed in seven additional prostate cancer case-control studies of individuals of European descent. In the combined case-control study group, the two SNPs revealed an OR = 1.24 (P = 2.57x10-10) for rs5945572 and OR = 1.15 (P = 2.23x10-6) for rs2710646. Combining the new data with the prior study strengthened these associations. The association between rs5945572 and prostate cancer risk was not related to early-onset or aggressive prostate cancer. However, the frequency of rs2710646 was higher in aggressive prostate cancer versus those with less aggressive disease, OR = 1.1 (P = 2.6x10-3). In summary, both SNPs were associated with prostate cancer, with estimated population attributable risks in individuals of European descent of 7% for rs5945572 (Xp11.22) and 5% for rs2710646 (2p15).
Efforts to identify additional variants associated with prostate cancer risk continue to be reported. Two genetic variants were reported to be associated with prostate cancer in a pooled case-control analysis from Iceland and Cancer Genetic Markers of Susceptibility (CGEMS). These SNPs include rs10934853 at 3q21.3 with an OR of 1.14 (P = 1.6 x 10-7) and rs8102476 at 19q13.2 with an OR of 1.12 (P = 1.6 x 10-11). A fine-mapping study identified two additional variants at 8q24 surrounding previously reported risk-associated SNPs. These include rs445114 with an OR of 1.14 (P = 3.1 x 10-8) and rs16902094 with an OR of 1.28 (P = 3.5 x 10-6). In addition, an effort to identify additional risk-associated variants at 11q13 identified the associtation of SNP rs11228565 with prostate cancer (OR = 1.23, P = 6.7 x 10-12). A GWAS follow-up study from the PRACTICAL Consortium reported seven new prostate cancer susceptibility loci on chromosomes 2, 4, 8, 11, and 22 (P = 1.6 x 10-8 to P = 2.7 x 10-33). More genetic variants of prostate cancer risk will likely be reported from such efforts and will need to be validated and clinically characterized.
In an exploratory, but relatively underpowered GWAS targeting aggressive prostate cancer, a SNP within DAB21P (a proposed prostate tumor suppressor gene) was associated with prostate cancer risk (OR = 1.27, 95% CI, 1.10–1.48; P = .0017). This is a novel finding but the analysis did not achieve genome-wide levels of statistical significance; replication in further studies is awaited.
Although the statistical evidence for an association between genetic variation at these loci and prostate cancer risk is overwhelming, the biologically relevant variants and the mechanism(s) by which they lead to increased risk are unknown and will require further genetic and functional characterization. Additionally, these loci are associated with very modest risk and more risk variants are likely to be identified in the future. Until their individual and collective influences on cancer risk are evaluated prospectively, their clinical relevance is unclear.
Most of the GWAS data generated to date on prostate cancer has been derived from populations of European descent. It is not known whether the genetic risk variants identified in Europeans will prove to be risk factors in non-European populations. Answering this generalizability question is complicated by a number of technical issues, such as known (and unknown) differences in linkage disequilibrium and minor allele frequencies between populations.
Genetic studies in large populations of non-European subjects are ongoing to address this question. Thirteen prostate cancer genetic risk variants were identified in prior GWAS among 2,768 prostate cancer cases and 2,359 controls from the Multiethnic Cohort (MEC). Study participants were of African American, European American, Latino, Japanese American, and Native Hawaiian ancestry. Their findings suggest that a large proportion of the genetic variants related to prostate cancer in populations of European ancestry were also related to prostate cancer risk in the MEC racial/ethnic populations and, further, that these variants appeared to act independently on prostate cancer risk. Specific variants were not associated with prostate cancer risk in one population subgroup or another. These exceptions were interpreted as indicating that the variants were not strongly linked (or perhaps not linked at all) to causal prostate cancer alleles in selected population subsets. The authors suggest that deep resequencing and fine-mapping of loci that display ethnic heterogeneity may represent a useful research strategy for localizing and identifying the alleles that truly cause prostate cancer.
Genetic Modifiers of Prostate Cancer Aggressiveness
Twenty prostate cancer risk SNPs identified in GWAS and fine-mapping follow-up studies were evaluated in 5,895 prostate cancer patients in search of SNP associations with prostate cancer aggressiveness. The risk-associated alleles of two SNPs (rs2735839 in KLK3 and rs10993994 in MSMB) were significantly associated with less aggressive prostate cancer; no significant associations were observed for the other 18 candidate SNPs. The two SNPs are known to be associated with PSA levels in normal men without prostate cancer. The authors concluded that the observed associations may be driven by over-representation within their case series of PSA screen-detected low-grade/low-stage disease, and that none of these risk-related SNPs appear to hold the potential for identifying men at increased genetic risk of more aggressive prostate cancer.
Polymorphisms and Prostate Cancer Susceptibility
The advent of large-scale high-throughput genotyping capabilities has resulted in an explosion of association studies between particular genes or genomic regions and prostate cancer risk. It is difficult to assess the import of any individual study. Accordingly, this PDQ Genetics of Prostate Cancer information summary will not attempt to provide an encyclopedic review of all such studies. Rather it will focus on studies that meet one or more of the following criteria: 1) Biological plausibility for the gene that is implicated; 2) Study designed with sufficient power to detect an odds ratio of an appropriate magnitude; 3) Multiple reports demonstrating the same association in the same direction; 4) Similar associations identified in studies of different design; 5) Evidence that the polymorphism is of functional significance; or 6) Existence of a prior hypothesis. However, individual studies may be cited by way of illustrating a specific theoretical point and do not imply that the association is definitive.
While many research teams have collected multiplex prostate cancer families with the goal of identifying rare, highly penetrant prostate cancer genes, other investigators have studied the potential roles of more common genetic variants as modifiers of prostate cancer risk. While these polymorphisms may not be associated with a large increase in relative risk, these variants may have a high population attributable risk because they are common. For example, if the population attributable risk of prostate cancer associated with a genetic variant was 10% among carriers, that would imply that 10% of prostate cancer could be explained by the presence of this variant among carriers. For a rare variant, the proportion of cancer in the POPULATION attributed to the variant would be much less than 10%. Thus, a small increase in the relative risk of prostate cancer associated with a genetic variant that occurs frequently in the general population might, theoretically, account for a larger proportion of all prostate cancers than would the effects of a mutation in a rare gene, such as HPC1. This fact has provided much of the stimulus for studying the role of common genetic variants in the pathogenesis of prostate cancer and other cancers.
Concerns have been raised that differences in ethnic composition (population stratification) may confound the results of some prostate cancer association studies because the incidence of prostate cancer varies according to ethnicity. If a polymorphism also exhibits different frequencies according to race, it may appear to be associated with the disease in the absence of a true causal relationship. This issue was explored in a study in which the CYP3A4-V allele appeared to be statistically associated with increased prostate cancer risk in African Americans (P = .007) and European Americans (P = .02), but not in Nigerians. However, when the investigators added ten markers at other chromosomal regions, the significance for CYP3A4-V in African American men was lost. When the P value above was corrected for the observed population stratification, it was no longer significant. Thus, population admixture and stratification can create false associations (and obscure true associations) between genetic polymorphisms and disease risk.
To minimize confounding by population stratification, family-based association methods can be used. An inverse association has been identified between a single nucleotide polymorphism (SNP) in the CYP17 gene and prostate cancer risk using a set of 461 discordant sibling pairs. Since the siblings are genetically related, population stratification cannot bias this finding. A study of 1,461 Swedish men in an ethnically homogenous population with prostate cancer compared with 796 control men confirmed an inverse association between a CYP17 variant and prostate cancer risk (P = .04).
In an effort to more comprehensively evaluate the relationship between genetic variants in a particular gene and the risk of a specific cancer, single SNP association studies are augmented by a haplotype-based analytical strategy, in which a series of closely linked SNPs is selected to represent the entire gene. The Multiethnic Cohort Study (MEC) investigators provide a recent example of this approach as it applies to prostate cancer. Twenty-nine SNPs were used to define four haplotypes spanning the IGF1 gene. The investigators observed modest statistically significant elevations in relative risk (ranging from 1.19–1.25) for each of the four haplotypes. They concluded that inherited variation in IGF1 may play a role in the risk of prostate cancer.
In addition to the specific examples cited above, there have been additional candidate genes examined for their potential roles in genetic susceptibility to prostate cancer. These include both systematic literature reviews [5,6,7] and formal meta-analyses evaluating specific candidate genes [8,9] on this complicated and evolving subject. Due to the cross-sectional nature of these studies, as well as the inconsistent results among reports targeting the same gene, these findings currently have no role in clinical decision making. The results of large, adequately powered, prospective analyses of these associations will be required.
Androgen Receptor Gene
Androgen receptor gene variants have been examined in relation to both prostate cancer risk and disease progression. The androgen receptor is expressed during all stages of prostate carcinogenesis. One study demonstrated that men with hereditary prostate cancer who underwent radical prostatectomy had a higher percentage of prostate cancer cells exhibiting expression of the androgen receptor and a lower percentage of cancer cells expressing estrogen receptor alpha compared with men with sporadic prostate cancer. The authors suggest that a specific pattern of hormone receptor expression may be associated with hereditary predisposition to prostate cancer.
Altered activity of the androgen receptor due to inherited variants of the androgen receptor gene may influence risk of prostate cancer. The length of the polymorphic trinucleotide CAG and GGN microsatellite repeats in exon 1 of the androgen receptor gene (located on the X chromosome) have been associated with the risk of prostate cancer.[12,13] Some studies have suggested an inverse association between CAG repeat length and prostate cancer risk, and a direct association between GGN repeat length and risk of prostate cancer; however, the evidence is inconsistent.[10,12,13,14,15,16,17,18,19,20,21,22] A meta-analysis of 19 case-control studies demonstrated a statistically significant association between both short CAG length (odds ratio [OR] = 1.2; 95% confidence interval [CI], 1.1–1.3) and short GGN length (OR = 1.3; 95% CI, 1.1–1.6) and prostate cancer; however, the absolute difference in number of repeats between cases and controls is less than 1, leading the investigators to question whether these small, statistically significant differences are biologically meaningful. Subsequently, the large MEC of 2,036 incident prostate cancer cases and 2,160 ethnically matched controls failed to confirm a statistically significant association (OR = 1.02; P = .11) between CAG repeat size and prostate cancer. A study of 1,461 Swedish men with prostate cancer compared with 796 control men reported an association between androgen receptor (AR) alleles with greater than 22 CAG repeats and prostate cancer (OR = 1.35; 95% CI, 1.08–1.69; P = .03).
The most recent analysis of androgen receptor CAG and CGN repeat length polymorphisms targeted African American men from the Flint Men's Health Study, in an effort to identify a genetic modifier that might help explain the increased risk of prostate cancer in black versus white males in the United States. This population-based study of 131 African American prostate cancer patients and 340 screen-negative African American controls showed no evidence of an association between shorter AR repeat length and prostate cancer risk. These results, together with data from three prior, smaller studies,[24,26,27] indicate that short AR repeat variants do not contribute significantly to the risk of prostate cancer in African American men.
5-Alpha-Reductase Gene (SRD5A2)
Molecular epidemiology studies have also examined genetic polymorphisms of the 5-alpha-reductase type II gene, which is also involved in the androgen metabolism cascade. Two isozymes of 5-alpha-reductase exist. The gene that codes for 5-alpha-reductase type II (SRD5A2) is located on chromosome 2. It is expressed in the prostate, where testosterone is converted irreversibly to dihydroxytestosterone (DHT) by 5-alpha-reductase type II. Evidence suggests that 5-alpha-reductase type II activity is reduced in populations at lower risk of prostate cancer, including Chinese and Japanese men.[29,30]
A polymorphism in the untranslated region of the SRD5A2 gene may also be associated with prostate cancer risk. Ten alleles fall into three families that differ in the number of TA dinucleotide repeats.[28,32] Although no clinical significance for these polymorphisms has yet been determined, some TA repeat alleles may promote an elevation of enzyme activity, which may in turn increase the level of DHT in the prostate.[10,28] A subsequent meta-analysis failed to detect a statistically significant association between prostate cancer risk and the TA repeat polymorphism, though a relationship could not be definitively excluded. This meta-analysis also examined the potential roles of two coding variants: A49T and V89L. An association with V89L was excluded, and the role for A49T was found to have at most a modest effect on prostate cancer susceptibility. Bias or chance could account for the latter observation. A study of 1,461 Swedish men with prostate cancer compared with 796 control men reported an association between two variants in SRD5A2 and prostate cancer risk (OR = 1.45; 95% CI, 1.01–2.08; OR = 1.49; 95% CI, 1.03–2.15).
Polymorphisms in several genes involved in the biosynthesis, activation, metabolism and degradation of androgens (CYP17, CYP3A4, CYP19A1, andSRD5A2) and the stimulation of mitogenic and antiapoptotic activities (IGF-1 and IGFBP-3) of normal prostate cells were examined for association with prostate cancer in 131 African American cases and 342 controls. While allele frequencies did not differ between cases and controls regarding three SNPs in the CYP17 gene (rs6163, rs6162, and rs743572), heterozygous genotypes of these SNPs were found to be associated with a protective effect (OR = 0.56; 95% CI, 0.35–0.88; OR = 0.57; 95% CI, 0.36–0.90; OR = 0.55; 95% CI, 0.35–0.88, respectively). Evidence suggestive of an association between SNP rs5742657 in intron 2 of IGF-1 was also found (OR = 1.57; 95% CI, 0.94–2.63). Additional studies are needed to confirm these findings.
Estrogen Receptor-Beta Gene
Other investigators have explored the potential contribution of the variation in genes involved in the estrogen pathway. A Swedish population study of 1,415 prostate cancer cases and 801 age-matched controls examined the association of SNPs in the estrogen receptor-beta (ER-beta) gene and prostate cancer. One SNP in the promoter region of ER-beta, rs2987983, was associated with an overall prostate cancer risk of 23% and a 35% risk for localized disease. This study awaits replication.
E-cadherin is a tumor suppressor gene in which germline mutations cause a hereditary form of gastric carcinoma. A SNP designated -160?A, located in the promoter region of E-cadherin, has been found to alter the transcriptional activity of this gene. Because somatic mutations in E-cadherin have been implicated in development of invasive malignancy in a number of different cancers, various investigators have searched for evidence that this functionally significant promoter might be a modifier of cancer risk. A meta-analysis of 26 case-controls studies evaluated this genetic variant as a candidate susceptibility allele for seven different cancers. Eight of these studies (~2,600 cases and 2,600 controls) evaluated the risk of prostate cancer. Overall, carriers of the -160?A allele were at 30% increased risk of prostate cancer (95% CI, 1.1–1.6) compared with controls. A second meta-analysis  of E-cadherin associations with prostate cancer, reported findings that were quite similar to those noted above, although the overall association between the -160?A allele was not statistically significant (OR = 1.21; 95% CI, 0.97–1.51). The second study was based on a set of individual studies which largely but not completely overlapped with those in the earlier report; it was the exclusion of a study judged to have inappropriate controls  that accounts for this difference. The overlap in individual studies included in these two meta-analyses is sufficiently large that the second meta-analysis does not represent confirmation of the first. Therefore, further studies are required to determine whether this finding is reproducible and biologically/clinically important.
Toll-like Receptor Genes
There is a great deal of interest in the possibility that chronic inflammation may represent an important risk factor in prostate carcinogenesis. The family of toll-like receptors has been recognized as a critical component of the intrinsic immune system, one which recognizes ligands from exogenous microbes and a variety of endogenous substrates. This family of genes has been studied most extensively in the context of autoimmune disease, but there also have been a series of studies which have analyzed genetic variants in various members of this pathway as potential prostate cancer risk modifiers.[40,41,42,43,44] The results have been inconsistent, ranging from decreased risk, to null association, to increased risk.
The current study was based upon 1,414 incident prostate cancer cases and 1,414 age-matched controls from the American Cancer Society Cancer Prevention Study II Nutrition Cohort. These investigators genotyped 28 SNPs in a region on chromosome 4p14 that includes TLR-10, TLR-1 and TLR-6, three members of the toll-like receptor gene cluster. Two TLR-10 SNPs and 4 TLR-1 SNPs were associated with significant reductions in prostate cancer risk, ranging from 29% to 38% for the homozygous variant genotype. A more detailed analysis demonstrated these 6 SNPs were not independent in their effect, but rather represented a single strong association with reduced risk (OR = 0.55; 95% CI, 0.33–0.90). There were no significant differences in this association when covariates such as Gleason score, history of benign prostatic hypertrophy, use of nonsteroidal anti-inflammatory drugs and body mass index were taken into account. This is the largest study undertaken to date, and included the most comprehensive panel of SNPs evaluated in the 4p14 region. While these observations provide a basis for further investigation of the toll-like receptor genes in prostate cancer etiology, inconsistencies with the prior studies and lack of information regarding what the biological basis of these associations might be, warrant caution in interpreting the findings.
Molecular epidemiology studies of prostate cancer have also examined associations with vitamin D receptor genes [46,47,48] and with SNP variants in phase I and phase II genes such as CYP1A1, CYP2D6, CYP17A2, CYP3A4, GST, and NAT1 and NAT2, with inconsistent results. A large meta-analysis studying GSTM1, GSTT1, and GSTP1 found a modest association between prostate cancer susceptibility and GSTM1 (OR = 1.33; 95% CI, 1.15–1.55). This association was seen in Caucasians and Asians but not in blacks. No association with prostate cancer risk was observed for GSTT1 or GSTP1.
An association between genetic variants in apoptotic genes and prostate cancer risk has been proposed. The BCL-2 gene has antiapoptotic functions. A case-control study found a 70% decrease in prostate cancer risk in European Americans with the -938AA genotype in the BCL-2 gene and an approximate 60% decrease in risk in Jamaican men of African descent with the 21G allele. Further studies are needed to confirm these findings.
Multiple Genes in Combination
A population-based, case-control study from Sweden found a cumulative association of five SNPs representing chromosomal regions 8q24, 17q12, and 17q24.3 to prostate cancer. Cases of prostate cancer (n = 2,893) were identified from four cancer registries in Sweden. Controls (n = 1,781) were randomly selected from the Swedish Population Registry and were matched to cases by age and geographic region. Sixteen SNPs from 8q24, 17q12, and 17q24.3 were analyzed, and due to strong linkage disequilibrium among SNPs in each region, one SNP with the strongest association to prostate cancer was selected to represent each region (rs4430796 at 17q12, rs1859962 at 17q24.3, rs16901979 at 8q24 [region 2], rs6983267 at 8q24 [region 3], and rs1447295 at 8q24 [region 1]). ORs for prostate cancer for men carrying any combination of one, two, three, or four or more genotypes associated with prostate cancer were estimated by comparing them with men carrying none of the associated genotypes using logistic regression analysis. Men who carried one to five SNPs had an increasing likelihood of having prostate cancer compared with men carrying none of the five SNPs (p for trend, 6.75x10-27). After controlling for age, geographic location, and family history of prostate cancer, men carrying four or more of these SNPs had a significant association to prostate cancer (OR = 4.47; 95% CI, 2.93–6.80; P = 1.20x10-13). When family history was added as a risk factor, men with five or more factors (five SNPs plus family history) had an even stronger association to prostate cancer (OR = 9.46; 95% CI, 3.62–24.72; P = 1.29x10-8). The population attributable-risks (PARs) for these five SNPs were estimated to account for 4% to 21% of prostate cancer cases in Sweden, and the joint PAR for prostate cancer of the five SNPs plus family history was 46%. These results support the belief that the genetic basis of prostate cancer is complex with variants from multiple genetic regions contributing to prostate cancer risk. Because the genes responsible for these associations remain unknown the biological basis for this complex relationship is unclear. Further the observations were made in a highly homogenous population raising concerns regarding the generalizability of the findings. In an era of increasing interest in polygenic risk this is a conceptually important study but its applicability to clinical practice is unclear.
Interventions in Familial Prostate Cancer
Refer to the PDQ summaries on Screening for Prostate Cancer; Prevention of Prostate Cancer; and Prostate Cancer Treatment for more information on interventions for sporadic nonfamilial forms of prostate cancer.
As with any disease process, decisions about risk-reducing interventions for patients with an inherited predisposition to prostate cancer are best guided by randomized controlled clinical trials, and by knowledge of the underlying natural history of the process. Unfortunately, little is known about either the natural history or the inherent biologic aggressiveness of familial prostate cancer compared with sporadic forms. Existing studies of the natural history of prostate cancer in men with a positive family history are predominantly based on retrospective case series. Because awareness of a positive family history can lead to more frequent work-ups for cancer and result in apparently earlier prostate cancer detection, assessments of disease progression rates and survival after diagnosis are subject to selection, lead time, and length biases. (Refer to the PDQ summary on Cancer Screening Overview for more information.)
Given the paucity of information on the natural history of prostate cancer in men with a hereditary predisposition, decisions about risk reduction, early detection, and therapy are currently based on the literature used to guide interventions in sporadic prostate cancer, coupled with the best clinical judgment of those responsible for the care of these patients, with the active participation of well-informed high-risk patients.
There are no definitive studies of primary prevention strategies in men with a hereditary risk of prostate cancer. Thus, there are no definitive recommendations that can be offered to these patients to reduce their risk for prostate cancer at the present time.
The Prostate Cancer Prevention Trial (PCPT), a prospective, randomized clinical trial of finasteride versus placebo, demonstrated a 25% reduction in prostate cancer risk among study participants receiving finasteride. Finasteride administration produced statistically similar reductions in prostate cancer risk in family history positive (19% decrease) and family history negative (26% decrease) subjects. A subsequent PCPT publication suggested that end-of-study biopsies in asymptomatic men with serum prostate-specific antigen (PSA) values consistently lower than 4.0 ng/mL were more likely to detect prostate cancer in men with an affected first-degree relative (19.7%) versus those with a negative family history (14.4%).
The concern over the reported increase of high-grade prostate cancer in the finasteride arm compared with the placebo arm (6.6% of men analyzed vs. 5.1%, respectively, P = .005) in the original report from the PCPT was recently reanalyzed with consideration of possible biases that may have influenced these findings. These biases included improved sensitivity of the PSA and digital rectal exam (DRE) for overall prostate cancer detection with finasteride, improved sensitivity of PSA for high-grade prostate cancer detection with finasteride, differences in participants reaching the study endpoints between the two arms, and increased detection of high-grade disease with finasteride due to reduction in size of the prostate gland. Using a bias-adjusted modeling analysis, 7,966 participants in the finasteride arm and 8,024 participants in the placebo arm of the PCPT were studied. No statistically significant difference was found in the overall prevalence of high-grade prostate cancer with finasteride compared with placebo (4.8% vs. 4.2%, respectively, P = .12). Further analysis in a subset of men with a prostate cancer diagnosis who were treated with radical prostatectomy (n = 500) revealed that men on finasteride had less high-grade prostate cancer compared with men who took placebo (6.0% vs. 8.2%, respectively). The estimated risk reduction for high-grade prostate cancer from this subset analysis in men who had a prostatectomy and took finasteride was 27% (relative risk [RR], 0.73; 95% confidence interval [CI], 0.56–0.96; P = .02).
Another study estimated the rate of true high-grade prostate cancer in the PCPT by extrapolating the Gleason score from the subset of participants who had a radical prostatectomy. Statistical modeling that accounted for misclassification of Gleason score from biopsy to radical prostatectomy was used in this study. When comparing finasteride with placebo, the estimated RR for low-grade and high-grade prostate cancer at prostatectomy was 0.61 (95% CI, 0.51–0.71) and 0.84 (95% CI, 0.68–1.05), respectively. Information was not reported as to whether men with a family history of prostate cancer had a reduction in high-grade prostate cancer in these analyses. Further definition of the prostate cancer prevention potential of finasteride in men with a family history of prostate cancer, along with genetic stratification to identify those men at truly increased risk for the disease, remains to be determined. Together these two studies suggest that the apparent excess risk of high-grade prostate cancer in men treated with finasteride is not substantiated. Rather, the apparent association may be explained by various biases not accounted for in the original analysis.
Level of Evidence: Iaii
Refer to the PDQ summary on Prevention of Prostate Cancer for a more detailed description of the prevention of prostate cancer in the general population. Information about ongoing prostate cancer prevention clinical trials is available from the NCI Web site.
There is little information about the net benefits and harms of screening men at higher risk of prostate cancer. There is no evidence to support specific screening approaches in prostate cancer families at high risk. Risks and benefits of routine screening in the general population are discussed in the PDQ summary on Screening for Prostate Cancer.
Prostate-specific antigen and digital rectal exam
There is limited information about the efficacy of commonly available screening tests such as the DRE or serum PSA in men genetically predisposed to developing prostate cancer. Furthermore, comparing the results of studies examining the efficacy of screening for prostate cancer is difficult; studies vary with regard to the cut-off values chosen for an elevated PSA test. For a given sensitivity and specificity of a screening test, the positive predictive value (PPV [proportion of men with positive tests who have prostate cancer]) increases as the underlying prevalence of disease rises. Therefore, it is theoretically possible that the PPV and diagnostic yield will be higher for the DRE and for PSA in men with a genetic predisposition than in average-risk populations.[4,5]
Currently, there are only a few case-control studies and no published randomized trials examining screening in men with an increased risk of prostate cancer. A 10-year longitudinal study of serum PSA and DRE every 6 to 12 months in high-risk men older than 40 years has been conducted. Two high-risk categories (1,227 men with a family history of prostate cancer and 1,224 African American men) were compared with 15,964 low-risk non–African American men without a family history of prostate cancer. Suspicious screening results were present in 7% of non–African American men with a family history of prostate cancer, 8% of the low-risk African American men, and 20% of African American men with a family history of prostate cancer. The PPV was inversely proportional to age for those who had an abnormal screening test and underwent biopsy. Among men aged 40 to 49 years, the PPV was 50% for non–African American men with a positive family history, 54% for African American men without a family history, and 75% among African American men with a family history, compared with 38%, 49%, and 52%, respectively, among men aged 50 years and older. Of the 16 cancers detected in high-risk men younger than 50 years, 15 were clinically significant, with intermediate Gleason scores (5–7), and three were not confined to the prostate.
One screening study of the relatives of 435 men with prostate cancer measured serum PSA every 12 months for 2 years. Four-hundred and forty-two participants were classified into two groups: sporadic (defined as only one first-degree relative with prostate cancer) or familial (with two or more cases of prostate cancer). PSA higher than 0.004 mg/L was present in 0.8% in men aged 40 to 49 years, compared with 12.4% of men older than 50 years. No differences in prostate cancer detection rates or elevated PSA levels were found between sporadic and familial groups. Of the ten prostate cancers detected in this study, nine were clinically localized and of intermediate Gleason scores (5–7).
In a Finnish prostate cancer screening study, family history of prostate cancer was obtained in 2,099 prostate cancer patients. This resulted in the identification of 103 prostate cancer families with two or more affected first-degree or second-degree relatives having at least one living first-degree unaffected male. From those families, 209 of 226 eligible first-degree unaffected asymptomatic males aged 45 to 75 years were enrolled in a study involving a single serum PSA measurement. An elevated PSA (2.6–28.3 mg/L) was identified in 21 (10%) of subjects. Subsequent biopsies revealed prostate adenocarcinoma in seven (3.3%), including one at an advanced stage, and two in prostatic intraepithelial neoplasia (1%). The mean age of PSA-detected cancers was 65.1 years, 7 years younger than the average age of prostate cancer diagnosis in Finland. In men with a family history of early-onset prostate cancer (mean age of diagnosis in the family <60 years), the frequency of elevated PSAs was 28.6% and subclinical prostate cancer was 14.3%, significantly higher than the 2.3% to 4.5% reported in other PSA screening studies of this type.[8,9,10,11,12,13] These findings, however, may not be comparable to U.S. studies: prostate screening practices may differ between Finland and the United States, and rates of prior screening in the population studied were not reported.
A large French Canadian study reported findings from 6,390 men older than 45 years who underwent prostate screening consisting of annual serum PSA and DRE followed by transrectal ultrasound imaging if an abnormality was detected. Of these, 1,563 (24.5%) were found to have an abnormal rectal exam (n = 504) or a PSA above 3.0 mg/L (n = 1,261). Twenty-six refused follow-up; of the remaining subjects, 50.5% underwent biopsy following ultrasound examination. Prostate cancer was identified in 264 men, representing 34.0% of those who underwent biopsy and 4.1% of all 6,390 enrolled subjects. The prevalence of screen-detected prostate cancer was highest in men reporting a brother with prostate cancer (10.21%), as opposed to those reporting a father with prostate cancer (4.75%). Overall in this study, the PPV of a PSA more than 3.0 mg/L was significantly associated with a family history. The PPV was 28.6% in men with a prostate cancer family history and 17.9% in men without an affected first-degree relative. The increase in PPV of PSA was confined to the men with a normal rectal exam.
A PSA screening study of 20,716 asymptomatic men identified by the Finnish population-based registry did not find a higher PPV for men with a family history of one or more first-degree relatives with prostate cancer, compared with controls. Using a PSA cut-off of 0.004 mg/L, the PPV of an abnormal PSA for the 964 men with a positive family history was 28% vs. 31% for the 19,347 men without a family history. The RR of developing prostate cancer among male relatives of men with prostate cancer was modest (RR = 1.3; 95% CI, 0.95–1.71), suggesting that the family history was not a significant prostate cancer risk factor in this study. This unexpected finding might account for the lack of differences seen in the PPV of the PSA test when comparing men with and without a family history of prostate cancer.
Prostate cancer detection was analyzed in 609 high-risk men, 231 Caucasian men with a family history of prostate cancer and 373 African American men of whom approximately 30% had a family history of prostate cancer. Using aggressive biopsy criteria, 9.0% of the Caucasian men and 9.1% of the African American men were diagnosed with prostate cancer. Twenty-two percent of the prostate cancers diagnosed were Gleason score 7 or higher and 20% of men diagnosed with prostate cancer had a prediagnosis PSA greater than 2.5 ng/mL. Further study is needed to define optimal screening measures in men with a family history of prostate cancer.
An analysis of data from the control arm of the PCPT yielded a prostate cancer risk model that incorporated PSA level, family history of prostate cancer, and DRE results to predict the likelihood that a man undergoing biopsy would have prostate cancer. Men younger than 55 years were not eligible for participation in this study; therefore, the usefulness of this model in the management of young men from prostate cancer families is not known.
Current recommendations for screening at-risk members of familial or hereditary prostate cancer kindreds are based on expert opinion panels.[17,18] Therefore, the overall summary of evidence related to the efficacy of screening is level 5. There are no randomized studies that address screening at-risk members of familial or hereditary prostate cancer kindreds, and the observational data are contradictory. Refer to the Screening Behaviors section of this summary for more information on factors that influence prostate cancer screening.
Level of Evidence: 5
Candidate prostate cancer biomarkers
Many new prostate cancer biomarkers (either alone or in combination) will be identified and proposed during the next 5 to 10 years. While this is an active area of research with a number of promising new biomarkers in early development, NONE OF THESE BIOMARKERS ALONE OR IN COMBINATION HAVE BEEN SUFFICIENTLY WELL-STUDIED TO JUSTIFY THEIR ROUTINE CLINICAL USE FOR SCREENING PURPOSES EITHER IN THE GENERAL POPULATION OR IN MEN AT INCREASED RISK OF PROSTATE CANCER BASED ON FAMILY HISTORY.
Before addressing information related to emerging prostate cancer biomarkers, it is important to consider the several steps that are required to develop and, more importantly, to validate a new biomarker. One useful framework was described by the National Cancer Institute (NCI) Early Detection Research Network investigators. These authors indicated that the goal of a cancer-screening program is to detect tumors at an early stage so that treatment is likely to be successful. The gold standard by which such programs are judged is whether the death rate from the cancer for which screening is performed is reduced among those being tested. In addition, the screening test must be sufficiently noninvasive and inexpensive to allow widespread use. Maintaining high test specificity (i.e., few false-positive results) is essential for a population screening test, because even a low false-positive rate results in many people having to undergo unnecessary and costly diagnostic procedures and psychological stress. It is likely that the use of several such cancer biomarkers in combination will be required for a screening test to be both sensitive and specific. Furthermore, a clinically useful test must have a high PPV (a parameter derived from sensitivity, specificity, and disease prevalence in the screened population). Practically speaking, a biomarker with a PPV of 10% implies that ten surgical procedures would be required to identify one case of prostate cancer; the remaining nine surgeries would represent false-positive test findings. In general, the prostate cancer research community considers biomarkers with a PPV less than 10% to be clinically unacceptable. Finally it is important to keep in mind that while novel biomarkers may be present in the sera of men with advanced prostate cancer (which comprise the vast majority of cases analyzed in the early phases of biomarker development), they may or may not be detectable in men with early stage disease. This is essential if the screening test is to be clinically useful in the detection of localized and potentially curable prostate cancer.
It has been suggested that there are five general phases in biomarker development and validation:
Phase I — Preclinical exploratory studies
- Identify potentially discriminating biomarkers.
- Usually done by comparing gene over- or under-expression in tumor compared with normal tissue.
- Since many exploratory analyses in large numbers of genes are performed at this stage, one or more may seem to have good discriminating ability between cancers and normal tissue by random chance alone.
Phase 2 — Clinical assay development for clinical disease
- Develop a clinical assay that can be obtained on noninvasively obtained samples (e.g., a blood specimen).
- Often the test targets the protein product of one of the genes found to be of interest in phase I.
- The goal is to describe the performance characteristics of the assay for distinguishing between subjects with and without cancer. At this point, the assay should be in its final configuration and remain stable throughout the following phases.
- IMPORTANT: Since the case subjects in a phase 2 study ALREADY HAVE CANCER, with assay results obtained at the time of disease diagnosis, one cannot determine if disease can be detected early with a given biomarker.
Phase 3 — Retrospective longitudinal repository studies
- Compare clinical specimens collected from cancer case subjects before their clinical diagnosis with specimens from subjects who have not developed cancer.
- Evaluate, as a function of time before clinical diagnosis, the biomarker's ability to detect preclinical disease.
- Define the criteria for a positive screening test in preparation for phase 4.
- Explore the influence of other patient characteristics (e.g., age, gender, smoking status, medication use) on the ability of the biomarker to discriminate between those with and without preclinical disease.
Phase 4 — Prospective screening studies
- Determine the operating characteristics of the biomarker-based screening test in a population for which the test is intended.
- Measure the detection rate (number of abnormal tests among all those with the disease) and the false-positive rate (the number of abnormal tests among all those who do not have the disease).
- Evaluate whether the cancers detected by the test are being found at an early stage, a point at which treatment is more likely to be curative.
- Assess whether the test is acceptable in a population of persons for whom it is intended. Will subjects comply with the test schedule and results?
Phase 5 — Cancer control studies
- Ideally, randomized controlled clinical trials in clinically relevant populations, in which one arm is subjected to screening and appropriate intervention if screen-positive, while the other arm is not screened.
- Determine whether the death rate of the cancer being screened for is reduced among those who use the screening test.
- Obtain information about the costs of screening and treatment of screen-detected cancers.
Finally, for a validated biomarker test to be considered appropriate for use in a particular population, it must have been evaluated in that specific population without prior selection of known positives and negatives. In addition, the test must demonstrate clinical utility, that is, a positive net balance of benefits and risks associated with the application of the test. These may include improved health outcomes, as well as net psychosocial and economic benefits.
Prostate cancer poses a further challenge relative to the potential impact of false-positive test results. There are no reliable noninvasive diagnostic tests for early-stage disease, and the value of identifying early-onset disease has not been established. This is further complicated by the fact that prostate cancer is clinically heterogeneous, that is, a proportion of prostate cancer may be relatively indolent disease of uncertain clinical significance. High test specificity (i.e., a very low false-positive rate) is required to avoid unnecessary screening and further diagnostic evaluation, which may include surgery.
New candidate prostate cancer SNPs have been identified and studied individually, in combination with family history, or in various other permutations. Most of the study populations are relatively small and comprise highly-selected known prostate cancer cases and healthy controls of the type evaluated in early development phases I and II. Results have not been consistently replicated in multiple studies; presently, none are considered ready for widespread clinical application.
Because individual single nucleotide polymorphisms (SNPs) have not met the criteria for an effective risk assessment test, it has been suggested that testing multiple prostate cancer-related SNPs may be required to obtain satisfactory results. An initial study evaluated five chromosomal regions associated with prostate cancer in a Swedish population, three at 8q24, one at 17q12 and one at 17q24.3. Sixteen SNPs within these regions were assessed in 2,893 men with prostate cancer and 1,781 controls. It was estimated that the five SNPs most strongly associated with prostate cancer accounted for 46% of prostate cancer in the Swedish men from this study. When considered independently, each SNP was associated with a small increase in prostate cancer risk. However, the investigators identified a cumulative stronger association with prostate cancer risk when multiple SNPs and family history were combined, versus men without any risk SNPs or a prostate cancer family history.
A larger study of 5,628 men with prostate cancer and 3,514 controls from the United States and Sweden, further strengthened this association. For men carrying one or more risk SNPs, the estimated odds ratio (OR) was 1.41 (95% Cl, 1.20–1.67) for one SNP to as high as 3.80 (2.77–5.22) for four or more SNPs. The cumulative effect of family history with up to five SNPs was estimated to have an OR of 11.26 (95% Cl, 4.74–24.75) for prostate cancer. The observation that family history added significant strength to the SNP-related association suggests that there may be additional genetic risk variants yet to be discovered. All available data to date are derived from studies of sporadic prostate cancer. Familial prostate cancer has not been evaluated.
Nineteen SNPs identified as candidate prostate cancer risk variants in GWAS studies were studied in 2,893 prostate cancer cases and 1,781 controls from Sweden, in an effort to identify a prostate cancer risk prediction model that did not include PSA. The final model included the presence of any 11 risk factors selected among 22 risk alleles from the 11 significant SNPs and family history. Its sensitivity and specificity were 0.25 and 0.86, respectively; these results are similar to those obtained for PSA from the Prostate Cancer Prevention Trial (i.e., 0.21 and 0.94, respectively). PSA itself could not be analyzed in the current report. The authors suggest that future studies should combine PSA with their model, to determine if this combination further improves prostate cancer risk prediction.
Viewed in the context of the criteria previously described, this five-SNP assay would be classified as phase 2 in its development. While this appears to be a promising avenue of prostate cancer risk evaluation, additional validation is required, particularly in an unselected population representative of the clinical population of interest.
Level of Evidence: 3
Numerous research groups are attempting to overcome the limited clinical utility of multiple SNP panels relative to prostate cancer risk by significantly expanding the number of SNPs in their models. A report describing 22 prostate cancer risk factor variants in a single population found that various combinations of these markers yielded prostate cancer OR greater than 2.5; however, these combinations occurred in only 1.3% of the population studied, illustrating how challenging it will be to find clinically useful SNP panels for this purpose. 
Various studies have shown better, worse, or similar survival rates after treatment in men with prostate cancer who have a family history of affected first-degree relatives, compared with those who have a negative family history.[26,27,28,29] There is extensive literature addressing whether family history of prostate cancer is linked with aggressive tumor behavior and consequently a worse prognosis. The most current longitudinal report suggests that this is not likely the case.
In general, there is insufficient information available to determine whether treatment strategies differ in efficacy for sporadic cases versus familial cases of prostate cancer. Decisions about treating familial cases of cancer are currently guided by information derived from therapeutic studies in the general population of prostate cancer patients. Therefore, no level of evidence is assigned. A detailed discussion of treatment in these patients is found in the PDQ Prostate Cancer Treatment summary, and information about ongoing prostate cancer treatment clinical trials is available from the NCI Web site.
Level of Evidence: Not assigned
Prostate Cancer Risk Assessment
The purpose of this section is to describe current approaches to assessing and counseling patients about susceptibility to prostate cancer. Genetic counseling for men at increased risk of prostate cancer encompasses all of the elements of genetic counseling for other hereditary cancers. (Refer to the PDQ summary on Cancer Genetics Risk Assessment and Counseling for more information.) The components of genetic counseling include concepts of risk for prostate cancer, reinforcing the importance of detailed family history, pedigree analysis to derive age-related risk, and offering participation in research studies to those individuals who have multiple affected family members.[1,2]Genetic testing for prostate cancer susceptibility is not available outside of the context of a research study. Families with prostate cancer can be referred to ongoing research studies; however, these studies will not provide individual genetic results to participants.
Prostate cancer will affect an estimated 1 in 6 American men over their lifetime. Currently, evidence exists to support the hypothesis that approximately 5% to 10% of all prostate cancer is due to rare autosomal dominant prostate cancer susceptibility genes.[3,4] The proportion of prostate cancer associated with an inherited susceptibility may be even larger.[5,6,7] Men are generally considered to be candidates for genetic counseling regarding prostate cancer risk if they have a family history of prostate cancer. The Hopkins Criteria provide a working definition of hereditary prostate cancer families. The three criteria include:
|1.||Three or more first-degree relatives (father, brother, son),|
|2.||Three successive generations of either the maternal or paternal lineages, and/or|
|3.||At least two relatives affected at age 55 years or younger.|
Families need to fulfill only one of these criteria to be considered to have hereditary prostate cancer. One study investigated attitudes regarding prostate cancer susceptibility among sons of men with prostate cancer. They found that 90% of sons were interested in knowing if there is an inherited susceptibility to prostate cancer and would be likely to undergo screening as well as consider genetic testing if there was a family history of prostate cancer; however, similar high levels of interest in genetic testing for other hereditary cancer syndromes have not generally been borne out in testing uptake once the clinical genetic test becomes available.
Risk Assessment and Analysis
Assessment of a man concerned about his inherited risk of prostate cancer should include taking a detailed family history, eliciting information regarding personal prostate cancer risk factors, documenting other medical problems, and evaluating genetics-related psychosocial issues.
Family history documentation is based on construction of a pedigree, and generally includes:
- The history of cancer in both maternal and paternal bloodlines.
- All primary cancer diagnoses (not just prostate cancer) and ages at onset.
- Race and ethnicity.
- Other health problems including benign prostatic hypertrophy.
(Refer to the Documenting the family history section in the PDQ summary on Cancer Genetics Risk Assessment and Counseling for a more detailed description of taking a family history.)
Analysis of the family history generally consists of four components:
|1.||Evaluation of the pattern of cancers in the family to identify cancer clusters, which might suggest a known inherited cancer syndrome. In addition to site-specific prostate cancer, other cancer susceptibility syndromes include prostate cancer as a component tumor (e.g., Hereditary Breast/Ovarian Cancer syndrome [associated with mutations in BRCA1 and BRCA2]).|
|2.||Assessment for genetic transmission. The pedigree should be assessed for evidence of both autosomal dominant and X-linked inheritance, which may be associated with a higher likelihood of an inherited susceptibility to prostate cancer. Autosomal dominant transmission is characterized by the presence of affected family members in sequential generations, with approximately 50% of males in each generation affected with prostate cancer. X-linked inheritance is suggested by apparent transmission of susceptibility from affected males in the maternal lineage. (Refer to the Analysis of the Family History section in the PDQ summary on Cancer Genetics Risk Assessment and Counseling for more information.)|
|3.||Age at onset of prostate cancer in family. An inherited susceptibility to prostate cancer may be likely in families with early-onset (inconsistently defined) prostate cancer. However, genetic research is also underway in families with an older age of prostate cancer onset. In the aggregate, the data are inconsistent relative to whether hereditary prostate cancer is routinely characterized by a younger-than-usual age at diagnosis.|
|4.||Risk assessment based on family and epidemiological studies. Multiple studies have reported that first-degree relatives of men affected with prostate cancer are two to three times more likely to develop prostate cancer than are men in the general population. In some studies, the relative risk of prostate cancer is highest among families who develop prostate cancer at an early age, consistent with other cancer susceptibility syndromes where early age at onset is a common feature. It has been estimated that male relatives of men diagnosed with prostate cancer younger than 53 years have a 40% lifetime cumulative risk of developing prostate cancer. A population-based case-control study of more than 1,500 cases and 1,600 controls, in which Caucasians, African Americans, and Asian Americans were studied, reported an odds ratio of 2.5 for men with an affected first-degree relative after adjusting for age and ethnicity. For men with a brother and father or son affected with prostate cancer, the relative risk was estimated to be 6.4.|
A number of studies have examined the accuracy of the family history of prostate cancer provided by men with prostate cancer. This has clinical importance when risk assessments are based on unverified family history information. In an Australian study of 154 unaffected men with a family history of prostate cancer, self-reported family history was verified from cancer registry data in 89.6% of cases. Accuracy of age at diagnosis within a 3-year range was correct in 83% of the cases, and accuracy of age at diagnosis within a 5-year range was correct in 93% of the cases. Self-reported family history from men younger than 55 years and reports about first-degree relatives had the highest degree of accuracy. Self-reported family history of prostate cancer, however, may not be reliably reported over time, which underscores the need to verify objectively reported prostate cancer diagnoses when trying to determine whether a patient has a significant family history.
The personal health and risk-factor history includes, but is not limited to:
- Family history.
- Current and past diet history, including fat intake.
- Current and past use of drugs that can affect prostatic growth, such as steroids (e.g., finasteride [Proscar]).
- Current and past use of complementary and alternative medications (e.g., saw palmetto, PC-SPES). (For more information on PC-SPES, refer to the PDQ complementary and alternative medicine summary on PC-SPES.)
The most definitive risk factors for prostate cancer are age, race, and family history. The correlation between other risk factors and prostate cancer risk is not clearly established. Despite this limitation, cancer risk counseling is an educational process that provides details regarding the state of the knowledge of prostate cancer risk factors. The discussion regarding these other risk factors should be individualized to incorporate the consultand's personal health and risk factor history. (For a more detailed description of prostate cancer risk factors, refer to the Risk Factors for Prostate Cancer section of this summary.)
The psychosocial assessment in this context might include evaluation of:
- Level of psychological distress.
- Perceived risk of prostate cancer.
- Past history of depression, anxiety, or other mental illness.
One study found that psychological distress was greater among men attending prostate cancer screening who had a family history of the disease, particularly if they also reported an overestimation of prostate cancer risk. Psychological distress and elevated risk perception may influence adherence to cancer screening and risk management strategies. Consultation with a mental health professional may be valuable if serious psychosocial issues are identified.
At this time, clinical genetic testing to detect inherited prostate cancer predisposition is not available. None of the candidate susceptibility genes have been unequivocally associated with prostate cancer predisposition. (Refer to the Prostate Cancer Susceptibility Loci section of this summary for more information.) For families suspected of having an inherited susceptibility to prostate cancer, participation in ongoing research studies investigating the genetic basis of inherited prostate cancer susceptibility can be considered.
Psychosocial Issues in Prostate Cancer
Research to date has included survey, focus group, and correlation studies on psychosocial issues related to prostate cancer risk. (Refer to the PDQ summary on Cancer Genetics Risk Assessment and Counseling for further information on psychological issues related to genetic counseling for cancer risk assessment.) Genetic testing for mutations in prostate cancer susceptibility genes, when testing becomes available, has the potential to identify those at highest risk, which facilitates risk-reducing interventions and early detection of prostate cancer. Having an understanding of the motivations of men who may consider genetic testing for inherited susceptibility to prostate cancer will help clinicians and researchers anticipate interest in testing. Further, these data will inform the nature and content of counseling strategies for men and their families, including consideration of the risks, benefits, decision-making issues, and informed consent for genetic testing.
Knowledge about risk for prostate cancer is thought to be a factor influencing men's decisions to pursue prostate cancer screening and, possibly, genetic testing. A study of 79 African American men (38 of whom had been diagnosed with prostate cancer; and the remainder who were unaffected but at high risk for prostate cancer) completed a nine–item telephone questionnaire assessing knowledge about hereditary prostate cancer. On a scale of 0 to 9, with 9 representing a perfect score, scores ranged from 3.5 to 9 with a mean score of 6.34. The three questions relating to genetic testing were the questions most likely to be incorrect. In contrast, questions related to inheritance of prostate cancer risk were answered correctly by the majority of subjects. Overall, knowledge of hereditary prostate cancer was low, especially concepts of genetic susceptibility, indicating a need for increased education. An emerging body of literature is now exploring risk perception for prostate cancer among men with and without a family history. Table 4 provides a summary of studies examining prostate cancer risk perception.
Table 4. Summary of Cross-Sectional Studies of Prostate Cancer Risk Perception
|Study Population||Sample Size||Proportion of Study Population That Accurately Reported Their Risk||Other Findings|
|Unaffected men with a family history of prostate cancer ||120 men aged 40 to 72 years||40%|
|First-degree male relatives (FDR of men with prostate cancer ||105 men aged 40 to 70 years||62%|
|Men with brothers affected with prostate cancer ||111 men aged 33 to 78 years||Not available||38% of men reported their risk of prostate cancer to be the same or less than the average man.|
|FDR of men with prostate cancer and a community sample ||56 men with a FDR with prostate cancer and 100 men without a FDR with prostate cancer all older than 40 years||57%||29% of men with a FDR thought that they were at the same risk as the average man, and 14% believed that they were at somewhat lower risk than average.|
Study conclusions vary regarding whether first-degree relatives of prostate cancer patients accurately estimate their prostate cancer risk. Some studies found that men with a family history of prostate cancer considered their risk to be the same as or less than that of the average man.[5,6] Other factors, including being married, have been associated with higher prostate cancer risk perception. A confounder in prostate cancer risk perception was confusion between benign prostatic hyperplasia and prostate cancer.
Anticipated Interest in Genetic Testing
A number of studies summarized in Table 5 have examined participants' interest in genetic testing, if such a test were available for clinical use. Factors found to positively influence the interest in genetic testing include:
- Advice of their primary care physician.
- Combination of emotional distress and concern about prostate cancer treatment effects.
- Having children.
Findings from these studies were not consistent regarding the influence of race, education, marital status, employment status, family history, and age on interest in genetic testing. The men studied expressed concerns about confidentiality of test results among employers, insurers, and family, as well as stigmatization, potential loss of insurability, and the cost of the test. These concerns are similar to those that have been reported in women contemplating genetic testing for breast cancer predisposition.[11,12,13,14,15,16] Concerns voiced about testing positive for a mutation in a prostate cancer susceptibility gene included decreased quality of life secondary to interference with sex life in the event of a cancer diagnosis, increased anxiety, and elevated stress.
Table 5. Summary of Cross-Sectional Studies of Anticipated Interest in Prostate Cancer Susceptibility Genetic Testing
|Study Population||Sample Size||Percent Expressing Interest in Genetic Testing||Other Findings|
|Prostate screening clinic participants ||342 men aged 40 to 97 years||89%||28% did not demonstrate an understanding of the concept of inherited predisposition to cancer|
|General population; 9% with positive family history ||12 focus groups with a total of 90 men aged 18 to 70 years||All focus groups|
|African American men ||320 men aged 21 to 98 years||87%||Most participants could not distinguish between genetic susceptibility testing and a prostate-specific antigen blood test|
|Men with and without first-degree male relatives with prostate cancer ||126 men older than 40 years; mean age 52.6 years||24% definitely; 50% probably|
|Swedish men with a FDR with prostate cancer ||110 men aged 40 to 72 years||76% definitely; 18% probably||89% definitely or probably wanted their sons to undergo genetic testing|
|Sons of Swedish men with prostate cancer ||101 men aged 21 to 65 years||90%; 100% of sons with 2 to 3 family members affected with prostate cancer||60% expressed worry about having an increased risk for prostate cancer|
|Healthy outpatient males with no history of prostate cancer ||400 men aged 40 to 69 years||82%|
|Healthy African American males with no history of prostate cancer ||413 African American men aged 40 to 70 years||87%||Belief in the efficacy of and intention to undergo prostate cancer screening was associated with testing interest|
|Healthy Australian males with no history of prostate cancer ||473 adult men||66% definitely; 26% probably||73% reported that they felt diet could influence prostate cancer risk|
Overall, these reports and a study that developed a conceptual model to look at factors associated with intention to undergo genetic testing  have shown a significant interest in genetic testing for prostate cancer susceptibility despite concerns about confidentiality and potential discrimination. These findings must be interpreted cautiously in predicting actual prostate cancer genetic test uptake once testing is available. In both Huntington disease and hereditary breast and ovarian cancers, hypothetical interest before testing was possible was much higher than actual uptake following availability of the test.[23,24]
Hereditary Prostate Cancer Families and Screening
The proportion of prostate cancers attributed to hereditary causes is estimated to be 5% to 10%, and the risk for prostate cancer increases with the number of blood relatives with prostate cancer and young age at onset of prostate cancer within families. There is considerable controversy in prostate cancer about the use of serum prostate-specific antigen (PSA) measurement and digital rectal exam (DRE) for prostate cancer early detection in the general population, with different organizations suggesting significantly different screening algorithms and age recommendations. (Refer to the PDQ summary on Prostate Cancer treatment for more information on prostate cancer in the general population, and the Interventions section of this summary for more information on inherited prostate cancer susceptibility.) This variation is likely to add to patient and provider confusion about recommendations for screening by members of hereditary cancer families or first-degree relatives of prostate cancer patients. Psychosocial questions of interest include what individuals at increased risk understand about hereditary risk, whether informational interventions are associated with increased uptake of prostate cancer screening behaviors, and what the associated quality-of-life implications of screening are for individuals at increased risk. Also of interest is the role of the primary care provider in helping those at increased risk identify their risk and undergo age- and family-history–appropriate screening. The literature on psychosocial aspects of hereditary prostate cancer is quite limited, but there are implications from even the small number of current studies for primary care practice.
In most cancers, the goal of improved knowledge of hereditary risk can be translated rather easily into a desired increase in adherence to approved and recommended (if not proven) screening behaviors. This is complicated for prostate cancer screening by the lack of clear recommendations for men in both high-risk and general populations. (Refer to the Screening section of this summary for more information.) In addition, controversy exists with regard to the value of early diagnosis of prostate cancer. This creates uncertainty for patients and providers and challenges the psychosocial factors related to screening behavior.
Several small studies have examined the behavioral correlates of prostate cancer screening at average and increased prostate cancer risk based on family history; these are summarized in Table 6. In general, results appear contradictory whether men with a family history are more likely to be screened than those not at risk, and whether the screening is appropriate for their risk status. Furthermore, most of the studies had relatively small numbers of subjects, and the criteria for screening were not uniform, making generalization difficult.
Table 6. Summary of Studies of Behavioral Correlates for Prostate Cancer Screening
|Study Population||Sample Size||Percent Undergoing Screening||Predictive Correlates for Screening Behavior|
|Unaffected men with at least one first-degree relative with prostate cancer.||82 men (aged =40 years; mean age 50.5 years).||PSA||Aged >50 years.|
|50% reported PSA screening within the previous 14 months.||Annual income =U.S. $40,000.|
|History of PSA screening prior to study enrollment.|
|Higher levels of self-efficacy and response efficacy for undergoing prostate cancer screening.|
|Sons of men with prostate cancer.||124 men (60 men with a history of prostate cancer aged 38–84 years, median age 59 years; 64 unaffected men aged 31–78 years, median age 55 years).||PSA||39.4% patient request.|
|Unaffected men: 95.3% reported ever having a PSA test.||35.6% physician request.|
|Affected men: 71.7% reported ever having a PSA test prior to diagnosis.|
|Unaffected men: 96.9% reported ever having a DRE.|
|Affected men: 91.5% reported ever having a DRE prior to diagnosis.|
|BOTH PSA AND DRE|
|Unaffected men: 93.8% had both.|
|Affected men: 70.0% reported having both prior to diagnosis.|
|Unaffected men with and without a first-degree relative with prostate cancer.||156 men aged =40 years (56 men with a first-degree relative; 100 men without a first-degree relative).||PSA||Older age.|
|63% reported ever having a PSA test.||First-degree relatives reported higher disease vulnerability and less belief in disease prevention, but this did not result in increased prostate cancer screening when compared to those without a first-degree relative.|
|86% reported ever having a DRE.|
|Unaffected Swedish men from families with a 50% probability of carrying a mutation in a dominant prostate cancer susceptibility gene.||110 men aged 50–72 years.||68% of men =50 years were screened for prostate cancer.||Greater number of relatives with prostate cancer.|
|Low score on the avoidance subscales of the Impact of Event Scale.|
|Brothers or sons of men with prostate cancer.||136 men aged 40–70 years (72% were African American men).||PSA||Greater number of relatives with prostate cancer.|
|72% reported ever having a PSA test.||Older age.|
|– 73% within 1 year.||Urinary symptoms.|
|– 23% 1–2 years ago.||71% reported their physician had spoken to them about prostate cancer screening.|
|– 4% >2 years ago.|
|90% reported ever having had a DRE.|
|– 60% within 1 year.|
|– 23% 1–2 years ago.|
|– 17% >2 years ago.|
|Unaffected men with and without a first-degree relative with prostate cancer.||166 men aged 40–80 years (83 men with a first-degree relative; 83 men with no family history).||PSA||Family history of prostate cancer.|
|First degree-relative: 72% reported ever having had a PSA test.||Greater perceived vulnerability to developing prostate cancer.|
|No family history: 53% reported ever having had a PSA test.|
|French brothers or sons of men with prostate cancer.||420 men aged 40–70 years.||PSA||Younger age.|
|88% adhered to annual PSA screening.||Greater number of relatives with prostate cancer.|
|Previous history of prostate cancer screening.|
|Unaffected African American men participating in a hereditary prostate cancer study and data from the 1998 and 2000 NHIS.||Unaffected men aged 40–69 years (134 men with a family history of =4 men with prostate cancer; 5,583 men from 1998 NHIS [for DRE] including 683 African American men and 4,900 Caucasian men; 3,359 men from 2000 NHIS [for PSA] including 411 African American men and 2,948 Caucasian men).||PSA||Younger age.|
|Family Study Cohort:||Fewer number of relatives with prostate cancer.|
|45% reported ever having had a PSA test.|
|African American men in NHIS:|
|65% reported ever having had a PSA test.|
|Family Study Cohort:|
|35% reported ever having had a DRE.|
|African American men in NHIS:|
|45% reported ever having had a DRE.|
Quality of Life in Relation to Screening for Prostate Cancer Among Individuals at Increased Hereditary Risk
CONCERN ABOUT DEVELOPING PROSTATE CANCER: Although up to 50% of men in some studies who were first-degree relatives of prostate cancer patients expressed some concern about developing prostate cancer, the level of anxiety reported is typically relatively low and is related to lifetime risk rather than short-term risk.[3,5] The concern is also higher in men who are younger than their first-degree relative was at the time when their prostate cancer was diagnosed. First-degree relatives who were unmarried worried more about developing prostate cancer than did married men. Men with higher levels of concern about developing prostate cancer also had higher estimates of personal prostate cancer risk and a larger number of relatives diagnosed with prostate cancer. In a Swedish study, only 3% of the 110 men surveyed said that worry about prostate cancer affected their daily life "fairly much," and 28% said it affected their daily life "slightly."
BASELINE DISTRESS LEVELS: Among men who self-referred for free prostate cancer screening, distress, both general and prostate cancer–related, did not differ significantly between men who were first-degree relatives of prostate cancer patients and men who were not. Men with a family history of prostate cancer in the study had higher levels of perceived risk. In a Swedish study, male first-degree relatives of prostate cancer patients who reported more worry about developing prostate cancer had higher Hospital Anxiety and Depression Scale (HADS) depression and anxiety scores than men with lower levels of worry. In that study, the average HADS depression and anxiety scores among first-degree relatives was at the 75th percentile. Depression was associated with higher levels of personal risk overestimation.
DISTRESS EXPERIENCED DURING PROSTATE CANCER SCREENING: A study measured the anxiety and general quality of life experienced by 220 men with a family history of prostate cancer while undergoing prostate cancer screening with PSA tests. In this group, 20% of the men experienced a moderate deterioration in their anxiety scores, and 20% experienced a minimal deterioration in health-related quality of life (HRQOL). The average period between assessments was 35 days, which encompassed PSA testing and a wait for results that averaged 15.6 days. Only men with normal PSA values (4 ng/mL or less) were assessed. Factors associated with deterioration in HRQOL included being aged 50 to 60 years, having more than two relatives with prostate cancer, having an anxious personality, being well-educated, and having no children presently living at home. These authors stress that analysis of the impact of screening on first-degree relatives should not rely solely on mean changes in scores, which may "mask diversity among responses, as illustrated by the proportion of subjects worsening during the screening process." Given that these were men receiving what was considered a normal result and that a subset of men experienced screening-associated distress, this study suggests that interventions to reduce screening-related distress may be needed to encourage men at increased hereditary risk to comply with repeated requests for screening.
A study in the United Kingdom assessed predictors of psychological morbidity and screening adherence in first-degree relatives of men with prostate cancer participating in a PSA screening study. One hundred twenty-eight first-degree relatives completed measures assessing psychological morbidity, barriers, benefits, knowledge of PSA screening, and perceived susceptibility to prostate cancer. Overall, 18 men (14%) scored above the threshold for psychiatric morbidity, consistent with normal population ranges. Cancer worry was positively associated with health anxiety, perceived risk, and subjective stress. However, psychological morbidity did not predict PSA screening adherence. Only past screening behavior was found to be associated with PSA screening adherence.
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Changes to This Summary (12 / 03 / 2009)
The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.
PROSTATE CANCER SUSCEPTIBILITY LOCI
Added text to state that there are more than three linkage disequilibrium blocks that have been demonstrated to contain loci that are independently associated with prostate cancer in the 8q region (cited Yeager et al. as reference 95 and Al Olama et al. as reference 96).
Added text about the significant excess risk of high-grade prostate cancer in Ashkenazi Jewish men with BRCA1 and BRCA2 mutations (cited Agalliu et al. as reference 126).
Included 2q21, 7q21, 8q11, 15q13-q14 , 17p12, 17q25, and 18q21 as additional chromosomal regions that may harbor prostate cancer susceptibility genes (cited Stanford et al. as reference 148).
Added text about a study that reported four additional genetic variants associated with prostate cancer (cited Gudmundsson et al. as reference 188). Also added text about a study that reported seven new prostate cancer susceptibility loci on chromosomes 2, 4, 8, 11, and 22 (cited Eeles et al. as reference 189).
Added Genetic Modifiers of Prostate Cancer Aggressiveness as a new section.
POLYMORPHISMS AND PROSTATE CANCER SUSCEPTIBILITY
Added text about a prostate cancer risk prediction model that does not include prostate-specific antigen (cited Zheng et al. as reference 24).
Added text to state that numerous research groups are attempting to overcome the limited clinical utility of multiple single nucleotide polymorphism (SNP) panels relative to prostate cancer risk by significantly expanding the number of SNPs in their models (cited Gudmundsson et al. as reference 25).
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Date Last Modified: 2009-12-03