Prostate cancer is a common and important health issue. Although effective treatment is often available for localized disease, metastatic prostate cancer remains incurable. The initial treatment for metastatic prostate cancer often includes medical or surgical treatments that deprive the tumor of male hormones (androgens) required for growth. Although this treatment is successful for many patients, the cancer may eventually return in others. Recurrent prostate cancer may be treated with additional hormonal agents, but these agents usually do not result in long-term control of the disease. Eventually most patients with recurrent prostate cancer progress to a state where the cancer grows despite very low level of circulating male hormones known as androgen independent prostate cancer (AIPC).