Patients who have received prior pelvic radiotherapy Prior pelvic radiotherapy or prostatectomy Previous pelvic radiotherapy Clinically large pelvic masses reaching above the umbilicus Pelvic organ prolapse greater than stage II Prior reconstructive pelvic surgery involving mesh for prolapse Histological or cytological confirmation of locally recurrent or metastatic rectal adenocarcinoma\r\n* Note: Patients with locally recurrent/persistent disease within the pelvis after primary therapy (chemotherapy, surgery, and/or radiotherapy) are eligible\r\n* Note: Patients who have had prior pelvic radiotherapy with a total dose of =< 54 Gy are eligible\r\n* Note: Patients with or without metastatic disease (excluding untreated central nervous system [CNS] metastasis), with primary pelvic disease or pelvic recurrence are eligible\r\n* Note: Patients with pelvic disease that is potentially resectable or unresectable are eligible Eligible patients should not have had previous pelvic radiotherapy, chemotherapy or surgery for prostate cancer Any size pelvic lymphadenopathy if it is thought to be a contributor to concurrent hydronephrosis Previous pelvic RT Prior pelvic radiotherapy Patients with any prior chemotherapy or radiotherapy for pelvic malignancy Candidate for pelvic or pelvic-inguinal radiotherapy and concurrent chemotherapy; patients undergoing preoperative chemoradiotherapy are excluded Patient with any prior chemotherapy or radiotherapy for pelvic malignancy Patient with any prior chemotherapy or radiotherapy for pelvic malignancy Completion of pelvic radiotherapy treatment for this current rectal cancer or any prior pelvic radiotherapy (e.g., prior prostate or cervical cancer therapy). Prior pelvic radiotherapy No prior pelvic radiotherapy Any previous pelvic radiotherapy Patients must not have received pelvic radiotherapy as treatment for primary or recurrent disease within 1 year of the first dose of study treatment. Subject who has undergone a prior pelvic anastomosis. Patients must be planned to receive whole pelvic radiotherapy to a total dose of 45 Gy or greater Patients who received prior pelvic radiotherapy for any indication History of any major rectal or pelvic surgery or radiotherapy Previous pelvic radiotherapy that would prevent prostate/seminal vesicle (SV) irradiation Previous pelvic radiotherapy Refuses or is unable to have pelvic MRI Subjects who have had previous pelvic radiotherapy or have had chemotherapy or surgery for prostate cancer Prior history of pelvic radiotherapy Any size pelvic lymphadenopathy if it is thought to be a contributor to concurrent hydronephrosis E 03. Prior isotope therapy, whole pelvic radiotherapy, or radiotherapy to >30% of bone marrow. Patients must not have undergone a prior partial cystectomy for invasive bladder cancer; patients must not have received any prior pelvic surgery that would obviate a complete extended lymphadenectomy (e.g. aorto-femoral/iliac bypass) or for whom the surgeon feels that their ability to perform a standard or extended pelvic node dissection would be compromised Pelvic osseous tumors ANY SIZE Acute pelvic inflammatory disease Has received and completed a course of pelvic radiotherapy ? 6 months prior to LAR surgery (Day 0). Candidate for pelvic, pelvic-inguinal, or extended field radiotherapy with or without concurrent chemotherapy; patients undergoing preoperative or adjuvant chemotherapy are excluded Patients with any prior pelvic surgery Patients with prior history of pelvic fractures or hip replacement Participants with a history of pelvic irradiation; or chemotherapy or radiotherapy within the preceding 14 days Patients must have had a pelvic MRI within 28 days prior to the initiation of treatment Prior breast, chest or pelvic radiotherapy Patients undergoing pelvic exenteration Radiotherapy within 28 days and abdominal/pelvic radiotherapy within 60 days prior to Day 1 of Cycle 1 Prior pelvic RT Known or suspected active pelvic infection Willingness to undergo pelvic radiotherapy Contraindications to radiotherapy (including active inflammatory bowel disease or prior pelvic radiation therapy [XRT]) Extra-pelvic metastasis on any imaging or biopsy. No prior pelvic radiotherapy Prior hip replacement or other major pelvic surgery Prior history of pelvic radiotherapy Past history of pelvic radiotherapy subjects with any contraindication to pelvic radiotherapy including, but not limited to, previous pelvic radiotherapy or brachytherapy