Inclusion Criteria:  Men age ≥ 18 with histologically confirmed prostate cancer after radical prostatectomy with a PSA ≥ 0.1 ng/mL Interval between prostatectomy and planned radiation therapy start date ≥ 6 months KPS ≥ 70 Patients with equivocal pelvic lymph nodes on imaging are eligible if the nodes are ≤ 1.5 cm in the short axis (equivocal evidence of metastatic disease outside of the pelvis on standard imaging requires documented negative biopsy) Ability to complete the EPIC-26 quality of life questionnaire Ability to obtain paraffin-embedded tissue block from radical prostatectomy specimens Ability to understand and the willingness to sign a written informed consent.  Exclusion Criteria:  Prior history of pelvic radiation therapy History of moderate/severe or active Crohn's disease or ulcerative colitis History of bladder neck or urethral stricture Evidence of distant metastatic disease or nodal involvement beyond the common iliac vessels Initiation of androgen deprivation therapy with a LHRH / GnRH agonist or antagonist greater than 6 months prior to enrollment or receipt of any non-LHRH / GnRH agonist or antagonist androgen deprivation or anti-androgen therapy History of another invasive malignancy within the previous 3 years except for adequately treated squamous or basal cell skin cancer Any condition that in the opinion of the investigator would preclude participation in this study