Hypofractionated Radiation Therapy or Conventional Radiation Therapy After Surgery in Treating Patients With Prostate Cancer

Inclusion Criteria: * PRIOR TO STEP 1 REGISTRATION * Adenocarcinoma of the prostate treated primarily with radical prostatectomy * Any type of radical prostatectomy will be permitted, including retropubic, perineal, laparoscopic, or robotically assisted; there is no time limit for the date of radical prostatectomy * One of the following pathologic T-classifications: pT2 or pT3 * Patients with positive surgical margins are eligible * One of the following pathologic N-classifications: pN0, pNX * If a lymph node dissection is performed, the number of lymph nodes removed per side of the pelvis and the extent of the pelvic lymph node dissection (obturator versus \[vs.\] extended lymph node dissection) should be noted whenever possible * No clinical evidence of regional lymph node metastasis * Computed tomography (CT) (with contrast if renal function is acceptable; a noncontrast CT is permitted if the patient is not a candidate for contrast), magnetic resonance imaging (MRI), nodal sampling, or dissection of the pelvis within 120 days prior to step 1 registration * Patients with pelvic lymph nodes equivocal or questionable by imaging are eligible if the nodes are =\< 1 cm in the short axis * A post-radical prostatectomy study entry PSA \>= 45 days after prostatectomy and within 30 days prior to step 1, \< 2.0 ng/mL * No evidence of a local recurrence in the prostate fossa based on a digital rectal examination (DRE) within 60 days prior to step 1 registration * Pat…