Cyproterone Acetate in Treating Patients With Newly Diagnosed Stage III or Stage IV Prostate Cancer

RATIONALE: Androgens can cause the growth of prostate cancer cells. Hormone therapy, such as cyproterone acetate may stop the adrenal glands from making androgens. Sometimes the tumor may not need treatment until it progresses. In this case, observation may be sufficient. It is not yet known whether giving cyproterone acetate continuously is more effective than giving cyproterone acetate after tumor progression in treating prostate cancer. PURPOSE: This randomized phase III trial is studying cyproterone acetate to compare how well it works when given continuously or after tumor progression in treating patients with newly diagnosed stage III or stage IV prostate cancer.