Stereotactic Body Radiotherapy for Prostate Cancer

Inclusion Criteria * History of histologically confirmed, clinical localized adenocarcinoma of the prostate treated with radical prostatectomy with definitive intent. * Presence of any ONE of the following: 1. Adverse pathologic features at the time of prostatectomy (positive surgical margin, pathologic T-stage 3-4 disease, pathologic Gleason score 8-10 disease, OR presence of tertiary Gleason grade 5 disease) 2. Documentation of rising prostate-specific antigen on at least two consecutive draws, with the magnitude of prostate-specific antigen exceeding 0.03 ng/mL 3. Intermediate- or high-risk Decipher genomic classifier score 4. Identification of prostate cancer in ≥1 lymph node at the time of prostatectomy (pN+ disease) * CT scan and MRI of the pelvis within 120 days prior to enrollment \[note: (a) if patient has medical contraindication to MRI, an exemption will be granted and enrollment can proceed; (b) for patients with PSA \<1.0 ng/mL, the treatment planning CT can substitute for a diagnostic CT scan; (c) a low-field, radiation planning MRI can replace the diagnostic MRI if the patient refuses or cannot obtain a high-field MRI\]. * Bone scan OR advanced nuclear imaging study within 120 days prior to enrollment for patients with PSA \>1.0 ng/mL. * Age ≥ 18. \~. KPS ≥ 70 and/or ECOG \<2. * Ability to understand, and willingness to sign, the written informed consent Exclusion Criteria * Patients with any evidence of distant metastases. Note, evidence of lymphadenopathy below the level of the renal arteries can be deemed loco regional per the discretion of the investigator. * Patients with neuroendocrine or small cell carcinoma of the prostate * Prior pelvic radiotherapy * History of Crohn's Disease, Ulcerative Colitis, or Ataxia Telangiectasia