Inclusion Criteria

DISEASE CHARACTERISTICS: Histologically confirmed unresectable, incompletely resected with
gross residual disease, or locally recurrent large bowel carcinoma confined to a site
within the abdomen or pelvis All disease must be encompassable within a single
radiotherapy port No evidence of uncontrolled metastatic disease outside of the planned
radiotherapy port

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: CALGB 0-2 Life expectancy:
Not specified Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count
at least 100,000/mm3 Hepatic: Bilirubin no greater than 2.0 mg/dL Renal: Not specified
Cardiovascular: No history of significant myocardial disease No New York Heart Association
class III or IV disease No unstable angina No myocardial infarction in the past 4 months
Other: No significant infection or other coexistent medical condition that would preclude
protocol therapy Maintain an adequate oral nutrition intake (at least 1,200 calories
estimated per day) No greater than 6 bowel movements per day prior to treatment No
significant nausea or emesis on optimal antiemetic therapy Not pregnant or nursing
Effective contraception required of all fertile patients

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior
irinotecan Endocrine therapy: Not specified Radiotherapy: No prior abdominal or pelvic
radiotherapy Surgery: At least 3 weeks since laparotomy or laparoscopic procedure with or
without resection