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. Combining more than one drug or combining radiation therapy with chemotherapy may kill more tumor cells. It is not yet known whether fluorouracil and mitomycin plus radiation therapy is more effective than fluorouracil and cisplatin plus radiation therapy for anal cancer. PURPOSE: This randomized phase III trial is studying fluorouracil and mitomycin plus radiation therapy to see how well it works compared to fluorouracil and cisplatin plus radiation therapy in treating patients with stage II or stage III anal cancer.