Radiation Therapy Plus Fluorouracil With or Without Additional Chemotherapy in Treating Patients With Primary Anal Cancer

RATIONALE: Radiation therapy uses high-energy x-rays to kill tumor cells. Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Combining chemotherapy with radiation therapy may kill more tumor cells. It is not yet known if fluorouracil plus radiation therapy is more effective with or without additional chemotherapy in treating anal cancer. PURPOSE: Randomized phase III trial to compare the effectiveness of fluorouracil plus radiation therapy with or without additional chemotherapy in treating patients who have primary anal cancer.