Postoperative or Salvage Radiotherapy for Node Negative Prostate Cancer Following Radical Prostatectomy

Inclusion Criteria

• Pathologically confirmed adenocarcinoma of the prostate treated primarily with open, laparoscopic or robotically assisted prostatectomy
• Pathological stage T2a-T3b (American Joint Committee on Cancer [AJCC] Criteria 8th edition [Ed.]) adenocarcinoma of the prostate
• Maximum prostate specific antigen (PSA) value of 20 ng/ml (after prostatectomy)
• At least one of the following risk factors as the indication for radiation: * If post-op radiotherapy: ** Extracapsular penetration ** Positive surgical margins ** Invasion of the seminal vesicles ** A persistently elevated post prostatectomy PSA (> 0.2 ng/ml that does not meet the definition of PSA recurrence, in the absence of detectable distant metastasis * If salvage radiotherapy: ** Biopsy proven and/or radiographically defined local-regional relapse ** Biochemical relapse after a non-detectable post prostatectomy PSA defined as a PSA that increases on 2 or more determinations to >0.03; or a persistent PSA elevation of >= 0.2 following prostatectomy, in the absence of detectable distant metastasis
• Eastern Cooperative Oncology Group (ECOG) performance status 0-1 within 90 days prior to study registration
• Patient must give study-specific informed consent on an Institutional Review Board (IRB)-stamped consent prior to any research related procedures or study treatment
• Patient must be at least 18 years old at the time of consent
• Hemoglobin >= 10 g/dl within 90 days prior to study registration
• Alkaline phosphatase within 90 days prior to study registration. If elevated, patient must have clinical correlation to assess for metastases. (Plain x-ray, CT, BALP and/or bone scan)
• History/physical examination with digital rectal examination and baseline toxicity assessment within 90 days prior to study registration

Exclusion Criteria

• Pathologic T1 tumors (AJCC Criteria 8th Ed.) tumors
• Evidence of distant metastasis or lymph node involvement pathologically or on imaging. If confirmatory imaging studies remain equivocal, the patient is excluded unless biopsy of the questionable area is negative
• Prior systemic chemotherapy for any reason
• Previous irradiation to the pelvis that would compromise the ability to deliver the prescribed study treatment (per treating physician discretion)
• Active inflammatory bowel disease (Crohn’s disease, diverticulitis or ulcerative colitis) affecting the rectum. (Non-active diverticulitis and Crohn’s disease not affecting the rectum are allowed)
• History of hip replacement
• Prior or concurrent cancer, other than non-melanomatous skin cancer, unless disease free for at least 5 years
• Taking Saw Palmetto or methotrexate and unable or unwilling to discontinue its use during radiation
• History of proximal urethral stricture requiring dilatation
• Any major medical, addictive or psychiatric illnesses which would affect the consent process, completion of treatment and/or interfere with follow-up. Consent by legal authorized representative is not permitted in this study