In this multicentre , open-label , randomised , phase 3 study we randomly assigned patients with rectal adenocarcinoma , clinically staged as cT3-4 or any node-positive disease , to two groups : a control group receiving standard fluorouracil-based combined modality treatment , consisting of preoperative radiotherapy of 504 Gy in 28 fractions plus infusional fluorouracil ( 1000 mg/m ( 2 ) on days 1-5 and 29-33 ) , followed by surgery and four cycles of bolus fluorouracil ( 500 mg/m ( 2 ) on days 1-5 and 29 ) ; or to an investigational group receiving preoperative radiotherapy of 504 Gy in 28 fractions plus infusional fluorouracil ( 250 mg/m ( 2 ) on days 1-14 and 22-35 ) and oxaliplatin ( 50 mg/m ( 2 ) on days 1 , 8 , 22 , and 29 ) , followed by surgery and eight cycles of oxaliplatin ( 100 mg/m ( 2 ) on days 1 and 15 ) , leucovorin ( 400 mg/m ( 2 ) on days 1 and 15 ) , and infusional fluorouracil ( 2400 mg/m ( 2 ) on days 1-2 and 15-16 ) .