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