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, 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 before or 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
Studies show that taking antiandrogens may provide a small benefit for men who have metastatic prostate cancer and are also taking an LH-RH agonist.1
All medicines have side effects. But many people don't feel the side effects, or they are able to deal with them. Ask your pharmacist about the side effects of each medicine you take. Side effects are also listed in the information that comes with your medicine.
Here are some important things to think about:
- Usually the benefits of the medicine are more important than any minor side effects.
- Side effects may go away after you take the medicine for a while.
- If side effects still bother you and you wonder if you should keep taking the medicine, call your doctor. He or she may be able to lower your dose or change your medicine. Do not suddenly quit taking your medicine unless your doctor tells you to.
Call 911 or other emergency services right away if you have:
- Trouble breathing.
- Swelling of your face, lips, tongue, or throat.
- Shortness of breath and chest pain.
Call your doctor if you have:
- Any signs of infection, such as a fever or chills.
- Breast pain or breast enlargement (gynecomastia).
- Problems with your vision or night vision.
- Swelling in your legs, ankles, or feet (edema).
- Yellowing of the skin or eyes (jaundice) or belly pain. This may mean the medicine has damaged your liver.
Common side effects of this medicine include:
- Hot flashes.
- Sexual problems, such as decreased sex drive or erection problems.
- Constipation or diarrhea.
- Dizziness or nausea.
- Fatigue or weakness.
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 a bisphosphonate specifically designed for people who are getting treatment for metastatic cancer.
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.
Medicine is one of the many tools your doctor has to treat a health problem. Taking medicine as your doctor suggests will improve your health and may prevent future problems. If you don't take your medicines properly, you may be putting your health (and perhaps your life) at risk.
There are many reasons why people have trouble taking their medicine. But in most cases, there is something you can do. For suggestions on how to work around common problems, see the topic Taking Medicines as Prescribed.
Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.
- Zelefsky MJ, et al. (2011). Cancer of the prostate. In VT DeVita Jr et al., eds., DeVita, Hellman and Rosenberg's Cancer: Principles and Practice of Oncology, 9th ed., pp. 1220–1271. Philadelphia: Lippincott Williams and Wilkins.
- National Comprehensive Cancer Network (2012). Prostate cancer. NCCN Clinical Practice Guidelines in Oncology, version 2.2012. Available online: http://www.nccn.org/professionals/physician_gls/f_guidelines.asp.
- Fizazi K, et al. (2011). Denosumab versus zoledronic acid for treatment of bone metastases in men with castration-resistant prostate cancer: A randomised, double-blind study. Lancet, 377(9768): 813–822.
Last Revised: September 12, 2012
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