 Based on these data the investigators proposed a phase III study, randomized, unblinded, adjuvant chemotherapy based on Fluorouracil5-FU and Oxaliplatin versus observation in patients with rectal adenocarcinoma T3-4, N0-1, M0 previously treated with neoadjuvant chemoradiotherapy and who did not presented complete response. The investigator believes that this subgroup of patients, who have not achieved complete response, will be benefit from adjuvant therapy. 