A Study of Shorter Course Hormone Therapy and Radiation for High-risk Prostate Cancer

Inclusion Criteria: * Pathologically-proven diagnosis of prostate adenocarcinoma * Clinical stage T3-4 or Gleason score 8-10 or PSA \>20 ng/ml °If radiographic T3-T4 is the only high-risk factor, it must be "consistent with" or \>90% probability of having T3-T4 disease determined by the reading radiologist. * Decipher genomic score ≤0.6 * Willing and able to provide written informed consent and Authorization for Use and Release of Health and Research Study Information (HIPAA authorization) * Age ≥18 * KPS ≥70 or ECOG 0-2 * Estimated life expectancy \>5 years * Baseline prostate volume ≤90 cc * Baseline IPSS ≤20 * No contraindications to ADT, brachytherapy, or pelvic external beam radiation therapy as determined by the treating radiation oncologist per standard practice * Patients who have already started ADT consisting of bicalutamide 50 mg PO daily with leuprolide or an equivalent GnRH analogue are eligible if given for ≤ 60 days prior to registration Exclusion Criteria: * Regional lymph node or metastatic disease * Prior pelvic radiation * Prior prostate surgery (including TURP or cryosurgery) * Prior history of inflammatory bowel disease * Unable to undergo anesthesia or brachytherapy * Active second malignancy or past history of malignancies diagnosed within the last 2 years that requires active therapy and/or in remission, with the exception of resected non-melanoma skin cancers, non-muscle invasive bladder cancer, stage I head and neck cancer, or stage I colorectal cancer