Inclusion Criteria

DISEASE CHARACTERISTICS:

- Diagnosis of metastatic colorectal adenocarcinoma incurable by surgery or not
amenable to radiotherapy with curative intent

- Progressive disease after one of the following prior treatments for metastatic
disease:

- Oxaliplatin-based chemotherapy

- Irinotecan and oxaliplatin combination chemotherapy

- 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

Hematopoietic:

- Absolute neutrophil count at least 2,000/mm^3

- Platelet count at least 100,000/mm^3

Hepatic:

- Bilirubin no greater than 0.5 mg/dL above upper limit of normal (ULN)

- AST no greater than 5 times ULN

Renal:

- Creatinine no greater than 1.5 times ULN

Cardiovascular:

- No unstable angina

- No symptomatic congestive heart failure

- No serious uncontrolled cardiac arrhythmia

Other:

- 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:

Biologic therapy:

- No concurrent sargramostim (GM-CSF)

Chemotherapy:

- See Disease Characteristics

- At least 4 weeks since prior chemotherapy

- No more than 1 prior chemotherapy regimen for advanced colorectal cancer

- Prior adjuvant chemotherapy allowed

Endocrine therapy:

- Not specified

Radiotherapy:

- See Disease Characteristics

- No prior radiotherapy to more than 25% of bone marrow

Surgery:

- See Disease Characteristics

- At least 4 weeks since prior major surgery