Antiandrogens for Prostate Cancer
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
Side effects from antiandrogen treatment may include:
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 receiving treatment for metastatic cancer.
One study found that men with metastatic prostate cancer who were treated with zoledronic acid had fewer bone problems and less pain than men who weren't treated with zoledronic acid. They also had a longer time before any bone problems began.2
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.
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