Fluorouracil, Leucovorin, and Irinotecan in Treating Patients With Recurrent or Refractory Metastatic Unresectable Colorectal Cancer

DISEASE CHARACTERISTICS: Histologically confirmed colorectal adenocarcinoma Metastatic, unresectable disease Meets 1 of the following criteria: At least 1 unidimensionally measurable metastatic lesion at least 10 mm by spiral scan OR 20 mm by conventional scan Evaluable disease Evidence of disease (e.g., ascites or bone metastases) by imaging techniques Progressive disease as defined by 1 of the following criteria: Progressive disease while receiving first-line chemotherapy Recurrent disease within 6 months after completing adjuvant chemotherapy No symptomatic brain metastases PATIENT CHARACTERISTICS: Age 18 to 80 Performance status WHO 0-2 Life expectancy At least 3 months Hematopoietic Absolute neutrophil count ≥ 1,500/mm^3 Platelet count ≥ 100,000/mm^3 Hepatic Bilirubin < 1.5 times upper limit of normal (ULN) Alkaline phosphatase < 3 times ULN Renal Not specified Cardiovascular No uncontrolled angina No myocardial infarction within the past 6 months Gastrointestinal No chronic diarrhea grade 2 or greater No unresolved fully or partially obstructed intestine Other Not pregnant or nursing Fertile patients must use effective contraception No other underlying disease or medical condition that would preclude study participation No other prior malignancy except curatively treated basal cell cancer or carcinoma in situ of the cervix No psychological, social, familial, or geographical condition that would preclude study follow-up PRIOR CONCURRENT THERAPY: Biologic therapy Not specified Chemotherapy See Disease Characteristics No prior irinotecan Endocrine therapy Not specified Radiotherapy At least 3 weeks since prior radiotherapy Surgery At least 3 weeks since prior surgery Other No other concurrent clinical trial participation