DISEASE CHARACTERISTICS:

* Histologically confirmed carcinoma of the anal canal, including any of the following subtypes:

* Squamous cell
* Basaloid
* Cloacogenic
* Primary invasive disease
* T2-4, N0-3 disease

* Clinically positive small inguinal nodes (i.e., < 1 cm in size) must be confirmed by biopsy (preferably fine-needle aspiration) within the past 6 weeks
* Biopsy is not required for enlarged inguinal, perirectal, or pelvic nodes on exam or CT scan that are found to be ≥ 1.0 cm and are considered to be clinically positive

PATIENT CHARACTERISTICS:

* Zubrod performance status 0-1
* Hemoglobin ≥ 8.0 g/dL (transfusion or other intervention allowed)
* ALT and AST < 3 times upper limit of normal
* Absolute neutrophil count ≥ 1,800/mm³
* Serum creatinine ≤ 1.5 mg/dL
* Platelet count ≥ 100,000/mm³
* Bilirubin < 1.4 mg/dL
* WBC ≥ 3,000/mm³
* INR ≤ 1.5
* No known AIDS

* HIV-positive patients without AIDS are eligible
* HIV test required for patients with clinical suspicion of AIDS
* No other invasive malignancy within the past 3 years except for nonmelanomatous skin cancer
* No severe, active comorbidity, defined as any of the following:

* Unstable angina and/or congestive heart failure requiring hospitalization within the past 6 months
* Transmural myocardial infarction within the past 6 months
* Acute bacterial or fungal infection requiring IV antibiotics
* Chronic obstructive pulmonary disease exacerbation or other respiratory illness requiring hospitalization or precluding study treatment
* Hepatic insufficiency resulting in clinical jaundice and/or coagulation defects
* Uncontrolled diabetes mellitus, uncompensated heart disease, and/or uncontrolled high blood pressure, that in the opinion of the patient's treating physician, requires an immediate change in management

* Patients may be eligible if appropriate changes in management have resulted in adequate control of the above mentioned conditions
* Other immunocompromised status (e.g., organ transplantation or chronic glucocorticoid use)
* Not pregnant or nursing
* Negative pregnancy test
* Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

* See Disease Characteristics
* No prior radiation therapy to the pelvis that would result in overlap of radiation therapy fields
* No prior systemic chemotherapy for cancer of the anus
* No prior surgery for cancer of the anus that removed all macroscopic anal cancer
* No concurrent sargramostim (GM-CSF)
* No concurrent amifostine