Two-fraction HDR Monotherapy for Localized Prostate Cancer

PRIMARY OBJECTIVES: I. To determine the safety of HDR monotherapy 13.5 Gy x 2 fractions delivered 3 hours apart in patients with low and intermediate risk prostate cancer. SECONDARY OBJECTIVES: I. To describe the prostate specific antigen (PSA) kinetics associated with HDR brachytherapy monotherapy 13.5 Gy x 2 fractions delivered 3 hours apart for low and intermediate risk prostate cancer. OUTLINE: Treatment will be administered on an outpatient basis. All treatment will be delivered over a single day. Participants will be followed for 6 months after last treatment or removal from study, or until death, whichever occurs first. Additional Follow up will be as per usual guidelines for prostate cancer, every 3 months following treatment with PSA for the first year, then every 4 months after year 2, and every 6 months after year 3 until 5 years of follow up are completed.