Combination of Nivolumab Immunotherapy With Radiation Therapy and Androgen Deprivation Therapy

Treatment with nivolumab will begin four weeks prior to the first brachytherapy treatment. Nivolumab will be given through a vein every 2 weeks for 4 courses. Nivolumab is a human immunoglobulin G4 (IgG4) monoclonal antibody that binds to the PD-1 receptor and blocks its interaction with PD-L1 and PD-L2, releasing PD-1 pathway-mediated inhibition of the immune response, including the anti-tumor immune response, resulting in decreased tumor growth.

High dose rate (HDR) Brachytherapy involves the delivery of a high dose of radiation, internally, directly to the prostate. This procedure is completed in one day as an outpatient procedure.

External beam radiation therapy to the participant's prostate will be given once a day, five days a week (Monday-Friday), for a total of five weeks. External radiation therapy treatments are given as an outpatient procedure and take about 10-15 minutes each day.

Standard of care.