Apalutamide With or Without Stereotactic Body Radiation in Treating Castration-Resistant Prostate Cancer

This phase II trial studies the how well apalutamide with or without stereotactic body radiation therapy work in treating participants with castration-resistant prostate cancer. Testosterone can cause the growth of prostate cancer cells. Hormone therapy using apalutamide may fight prostate cancer by blocking the use of testosterone by the tumor cells. Stereotactic body radiation therapy uses special equipment to position a patient and deliver radiation to tumors with high precision. This method can kill tumor cells with fewer doses over a shorter period and cause less damage to normal tissue. It is not yet known whether giving apalutamide with or without stereotactic body radiation therapy works better in treating participants with castration-resistant cancer.