Gemcitabine in Treating Patients With Advanced Colorectal Cancer

DISEASE CHARACTERISTICS: Histologically confirmed advanced colorectal cancer that has failed at least 1 prior course of fluoropyrimidine-based chemotherapy Measurable and/or evaluable disease PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * 0-2 Life expectancy: * At least 3 months Hematopoietic: * WBC at least 3,000/mm3 * Platelet count at least 100,000/mm3 Hepatic: * Bilirubin no greater than 2.5 times upper limit of normal (ULN) * ALT and/or AST no greater than 3 times ULN (no greater than 10 times ULN if * secondary to hepatic involvement by tumor Renal: * Creatinine no greater than 2.0 mg/dL Cardiovascular: * No history of cardiac arrhythmias requiring chronic treatment beyond an * acute event (e.g., arrhythmias during severe electrolyte abnormalities * allowed) * No active cardiac disease requiring treatment other than hypertension, * stable angina, or chronic valvular disease Other: * No other malignancy within the past 5 years except curatively treated * (including surgically cured) cancer * No serious medical or psychiatric illness that would preclude study * No active uncontrolled bacterial, fungal, or viral infection * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: * Not specified Chemotherapy: * See Disease Characteristics * No more than 3 prior chemotherapy regimens * Must have 1 prior fluorouracil-based regimen and 1 other cytotoxic agent * (e.g., irinotecan) * More than 4 weeks since prior chemotherapy * Prior gemcitabine allowed * No other concurrent antineoplastic therapy Endocrine therapy: * Not specified Radiotherapy: * More than 4 weeks since prior radiotherapy Surgery: * More than 4 weeks since prior surgery