Antiandrogens for prostate cancer
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How It Works
Androgens are hormones. Antiandrogens are drugs that block the action of these hormones. In prostate cancer, they block the action of testosterone made by the testicles and/or adrenal glands. This usually slows prostate cancer growth.
There are steroidal antiandrogens and "pure" antiandrogens. The steroidal antiandrogens include megestrol (Megace). The "pure" or nonsteroidal antiandrogens include bicalutamide (Casodex), flutamide (Eulexin), and nilutamide (Nilandron).
Why It Is Used
An antiandrogen is often added to luteinizing hormone-releasing hormone (LH-RH) agonist therapy to prevent a rise in testosterone at the beginning of LH-RH agonist therapy. (The rise in testosterone can cause a tumor flare with bone pain, urinary blockage, or other symptoms of rapid cancer growth. But this growth does shrink over time.)
Antiandrogens can be used along with surgery to remove the testicles (orchiectomy).
Antiandrogens may be used 2 months before radiation or from 4 months to 2 years after radiation for men with intermediate-risk prostate cancer.
Antiandrogens are often used in combination with other hormone therapy to block the supply of testosterone. This is done to slow the growth of advanced prostate cancer and ease severe bone pain caused by the spread of cancer to the bones.
How Well It Works
Antiandrogen therapy by itself is not an effective treatment for advanced prostate cancer.1 But it does help other treatments work better.
For men with intermediate-risk prostate cancer, antiandrogen therapy may be used 2 months before radiation or from 4 months to 2 years after radiation treatment.
Antiandrogen treatment after surgery to remove the prostate (radical prostatectomy) can slow the growth of cancer near the prostate and can increase survival.1
Antiandrogen treatment for 2 to 3 years after radiation therapy increases survival for some men who have advanced prostate cancer.1
Side effects from antiandrogen treatment may include:
- Breast enlargement (gynecomastia).
- Low red blood cell count (anemia).
- Decreased sex drive.
- Erection problems.
- Liver problems. Some cases of serious liver problems have been reported.
Long-term treatment with antiandrogens may cause osteoporosis, which causes bones to become brittle and break more easily. Your doctor may prescribe a bisphosphonate medicine. Zoledronic acid is specifically designed for people who are receiving treatment for metastatic cancer. In a clinical trial of men with metastatic prostate cancer, men who took zoledronic acid experienced far fewer bone fractures and less bone pain than those who did not take the drug.1 For more information on prevention of and medicine for bone thinning, see the topic Osteoporosis.
See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)
What To Think About
Antiandrogens may improve a man's quality of life when bone pain caused by prostate cancer is severe.
Sometimes flutamide has an effect called a “withdrawal response” in which the tumor shrinks and the PSA level improves when a man stops taking the medicine.
Last Updated: July 1, 2008