Treating Advanced Prostate Cancer
Combination Radiation and Endocrine Therapy
Sometimes, patients receive endocrine therapy in combination with external beam radiation therapy for the treatment of prostate cancer. This treatment uses a high-energy X-ray machine to direct radiation to the prostate tumor. For patients with intermediate or high risk prostate cancer, studies show this combination is more effective at slowing the disease than endocrine therapy or radiation therapy alone.
Radiation can also come in the form of a monthly intravenous drug called Xofigo. Xofigo is approved for use in men who have advanced prostate cancer that has spread only to the bones. Candidates should have also received therapy designed to lower testosterone. The drug works by binding to minerals within bones to deliver radiation directly to bone tumors. A study of 809 men showed that those taking Xofigo lived an average of 3 months longer than those taking a placebo.
Secondary Endocrine Therapy
At some point, PSA levels begin to rise despite treatment with endocrine therapy. This signals that endocrine therapy is no longer working to reduce testosterone levels in the body. When this happens, doctors may decide to make changes to the endocrine therapy. This is called secondary hormone therapy. It can be done in a number of ways. For instance, if you have had surgery to remove your testicles, your doctor may suggest that you begin taking an anti-androgen. If you have been using combination therapy that involves an anti-androgen and LHRH analogs, your doctor may stop the use of the anti-androgen. This is known as anti-androgen withdrawal. Another option is to change the type of hormone drug. However, the use of an LHRH drug must be continued to prevent a testosterone rebound from stimulating the growth of prostate cancer cells.
Abiraterone is a new anti-androgen drug. It is indicated for use in prostate cancer with prednisone after progression of prostate cancer while receiving docetaxel. It's also used upon progression after completion of a docetaxel chemotherapy regimen.
Ketoconazole, an antifungal agent, inhibits adrenal and testicular synthesis of testosterone when used at high doses. Response rates in a second line setting are 20%-40% with significant side effects. Doses range from 200 mg 3 times a day to 400 mg three times a day. The drug must be given with hydrocortisone to prevent adrenal insufficiency.
Diethylstilbestrol (DES) inhibits testicular synthesis of testosterone. It must be at high doses (3 mg/day), which causes side effects. It is rarely used today.
A newer therapy, MDV-3100 is currently under study.
Standards of Care in Hormone Therapy
Most doctors agree that endocrine therapy is the most effective treatment available for patients with advanced prostate cancer. However, there is disagreement on exactly how and when endocrine therapy should be used. Here are a few issues regarding standards of care: