Enzalutamide + External Beam Rt For Prostate

This research study is evaluating a drug called enzalutamide in combination with external beam radiation therapy as a possible treatment for prostate cancer. Presently, when participants receive hormonal therapy with radiation therapy for prostate cancer, medications are given to reduce testosterone levels in the blood stream. This leads to side effects such as loss of sex drive, erectile dysfunction (ED) and decrease in muscle strength. The purpose of this study is test another form of hormonal therapy with radiation therapy. The medication called enzalutamide will be used with radiation therapy. Instead of lowering testosterone, enzalutamide blocks testosterone in cells. This study will test if enzalutamide when used with radiation will lower the PSA without causing the side effects associated with medications that lower testosterone in the blood stream.