Combination Chemotherapy Plus Radiation Therapy in Treating Patients With Stage II or Stage III Anal Cancer
RATIONALE: Drugs used in chemotherapy 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. Combining chemotherapy with radiation therapy may kill more tumor cells. PURPOSE: This randomized phase III trial is studying different regimens of giving combination chemotherapy together with radiation therapy and comparing how well they work in treating patients with stage II or stage III anal cancer.