Comparison of Adjuvant Chemotherapy Regimens in Treating Stage II/III Rectal Cancer

This randomized phase III trial is comparing the effectiveness of three adjuvant combination chemotherapy regimens in treating patients who are receiving radiation therapy and fluorouracil either before or after surgery for stage II or stage III rectal cancer. Drugs used in chemotherapy, such as irinotecan, fluorouracil, leucovorin, and oxaliplatin, use different ways to stop tumor cells from dividing so they stop growing or die. Radiation therapy uses high-energy x-rays to damage tumor cells. It is not yet known which adjuvant combination chemotherapy regimen is more effective in treating patients who are receiving radiation therapy and fluorouracil either before or after surgery for rectal cancer.