Imaging Studies to Check the Local Response of Prostate Cancer to Radiation Therapy

Background: \- Radiation is a common treatment for prostate cancer. It helps damage tumor cells and causes them to die. Radiation can be effective, but some tumors may be harder to treat with radiation or even with surgery. This happens to a small number of men who have either radiation or surgery for prostate cancer. Most men who have these hard-to-treat tumors do not know if the tumor has recurred only in the prostate or has spread to another area. Also, men whose prostate cancer has recurred only after radiation may have different treatment options. This study will use improved imaging studies to better understand why some men do not respond as well to initial radiation treatments. Objectives: \- To use detailed imaging studies to look at the results of local radiation therapy for prostate cancer. Eligibility: * Men at least 18 years of age who are scheduled to have radiation for prostate cancer. * Men at least 18 years of age whose prostate cancer has returned after earlier treatments. Design: * All participants will have a medical history and physical exam. Blood and urine samples will be collected. Imaging studies will be used to evaluate the cancer at the start of the study. * All participants will have an initial full magnetic resonance imaging (MRI) scan of the prostate. Tumor and healthy tissue samples will be collected. * Those whose cancer has recurred after treatment will discuss possible treatment options with the study doctors. * Participants who are scheduled to have radiation will have radiation therapy. This will be given according to the current standard of treatment. * After radiation, participants will have regular follow-up tests and imaging studies. They will have another full MRI scan 6 months after the end of radiation treatment.