Inclusion Criteria

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