Multi-omic Approach to Study HDR Brachytherapy for Favorable Risk and Low Tier Intermediate Risk Prostate Cancer

Inclusion Criteria: * Favorable risk and intermediate-risk prostate cancer with estimated life expectancy of at least 10 years. * Clinical stage T1c-T2b, PSA \< 20, Gleason \< 8 * ECOG 0-1 * Low tier intermediate-risk prostate cancer is defined by: a single NCCN intermediate risk factor (either Gleason 7(3+4) and PSA \< 10 ng/ml OR Gleason 6 and PSA 10-20 ng/ml) * Extensive favorable-risk disease is defined as: clinical stage T1c-T2a, PSA \< 10, Gleason 6, ≥ 50% of biopsy cores containing cancer, PSA density \> 0.2 ng/cc, * Selected intermediate risk patients not defined above * T1c/T2a * PSA \< 10 and Gleason 4+3 * PSA \> 10 (\< 20) and Gleason 3+4 * PSA 10-15 ng/ml and Gleason 4+3 and \< 33% cores involved * Max tumor length in any core 10 mm * No androgen deprivation therapy (ADT) * Signed study specific informed consent. Exclusion Criteria: * Prior radical surgery for carcinoma of the prostate, * Prior pelvic radiation * Prior chemotherapy for prostate cancer, * Claustrophobic or unable to undergo MRI * Patients unsuitable for general anesthesia, on blood thinners which cannot be stopped for 24 hours, or who have contraindications to radiotherapy such as systemic sclerosis, or inflammatory bowel disease