Chemotherapy Plus Radiation Therapy in Treating Patients With Stage II or Stage III Anal Cancer

DISEASE CHARACTERISTICS: * Histologically confirmed primary squamous, basaloid, or cloacogenic carcinoma of the anal canal, other than carcinoma in situ * T2-4, Any N, M0 (stage II or III) * No local or regional recurrence after local excision or abdominal peritoneal resection PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * Karnofsky 60-100% Life expectancy: * Not specified Hematopoietic: * WBC at least 4,000/mm\^3 * Absolute neutrophil count at least 1,800/mm\^3 * Platelet count at least 100,000/mm\^3 * Hemoglobin at least 10 g/dL Hepatic: * Bilirubin less than 1.4 mg/dL Renal: * Creatinine no greater than 1.5 mg/dL OR * Creatinine clearance at least 80 mL/min Cardiovascular: * No uncompensated heart disease * No uncontrolled high blood pressure Other: * No AIDS * No active systemic infection * No uncontrolled diabetes * No other prior malignancy within the past 5 years except nonmelanoma skin cancer * No mental condition that would preclude study participation * Not pregnant or nursing * Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: * Prior epoetin alfa allowed in lieu of blood transfusions Chemotherapy: * At least 5 years since prior chemotherapy Endocrine therapy: * Not specified Radiotherapy: * At least 5 years since prior radiotherapy Surgery: * No prior surgery of anal canal except for biopsy of study site