- Histologically-confirmed adenocarcinoma of the rectum. Clinical stages T3; T4; or N1 as determined by endoscopic ultrasound; or a rectal CT or MRI scan are eligible, including T3 N0; T3 N1; T4 N0; T4 N1; T1-4 N1. Rectal cancers are defined as those whose distal border extends to within 12 cm of the anal verge.