Combination Chemotherapy in Treating Patients With Metastatic Colorectal Cancer Previously Treated With Irinotecan

DISEASE CHARACTERISTICS: Diagnosis of metastatic colorectal adenocarcinoma incurable by surgery or not amenable to radiotherapy with curative intent Progressive disease no more than 3 months after completion of a prior weekly irinotecan, fluorouracil, and leucovorin calcium chemotherapy regimen At least 1 measurable lesion At least 20 mm in at least one dimension No known CNS metastases or carcinomatous meningitis PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: At least 12 weeks Absolute neutrophil count greater than 2,000/mm3 Platelet count at least 100,000/mm3 Bilirubin no greater than 0.5 mg/dL above upper limit of normal (ULN) AST no greater than 5 times ULN Creatinine no greater than 1.5 times ULN OR creatinine clearance greater than 60 mL/min No unstable angina No symptomatic congestive heart failure No serious uncontrolled cardiac arrhythmia No active or uncontrolled infection No evidence of other serious illness No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer or noninvasive carcinomas Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: No concurrent sargramostim (GM-CSF) At least 4 weeks since prior chemotherapy No more than 1 prior chemotherapy regimen for advanced colorectal cancer Prior adjuvant chemotherapy allowed No prior radiotherapy to more than 25% of bone marrow At least 4 weeks since prior major surgery