Inclusion Criteria:

          -  Patient has diagnosis of pathologically confirmed prostate cancer, treated with
             radical prostatectomy. Any type of radical prostatectomy will be permitted, including
             retropubic, perineal, laparoscopic, or robotically assisted

          -  Patient has pathologic T2N0M0 or T3N0M0 stage

          -  Patient diagnosed with Gleason score of 6-10

          -  For patients radiated in the adjuvant setting: pathology demonstrates positive margin,
             extracapsular extension, or seminal vesicle involvement without detectable prostate
             specific antigen (PSA) (PSA of 0.0)

          -  For patients radiated in the salvage setting: pathology demonstrates positive margin,
             extracapsular extension, seminal vesicle involvement with detectable PSA of > 0.1

          -  Eastern Cooperative Oncology Group (ECOG) performance 0-2

          -  Patients may receive 6 months and up to 24 months of androgen deprivation therapy.
             Patients may have received androgen deprivation therapy up to 6 months prior to
             postoperative radiotherapy

          -  If the patient has a prior history of any cancer other than prostate cancer, he must
             have completed treatment within 1 year of study registration and the patient must have
             no evidence of disease of this prior non-prostate cancer

        Exclusion Criteria:

          -  Any evidence of nodal positivity beyond pathologic stage pN0

          -  Prior radiation therapy to prostate/seminal vesicle fossa or postoperative region

          -  Neoadjuvant chemotherapy before or after prostatectomy

          -  History of lupus, scleroderma, or calcinosis, Raynaud's phenomenon, esophageal
             dysmotility, sclerodactyly, and telangiectasia (CREST) syndrome

          -  History of severe active co-morbidity

          -  Unstable angina and/or congestive heart failure requiring hospitalization within the
             last 6 months

          -  Transmural myocardial infarction within the last 6 months

          -  Severe hepatic disease, defined as a diagnosis of Child-Pugh class B or C hepatic
             disease

          -  End-stage renal disease (i.e., on dialysis or dialysis has been recommended)