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