Inclusion Criteria

DISEASE CHARACTERISTICS: Histologically confirmed advanced or metastatic adenocarcinoma of
the colon and rectum Surgically unresectable disease Measurable disease Disease outside
the prior radiotherapy port and/or progressive disease within the previously irradiated
volume

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy:
Not specified Hematopoietic: WBC at least 3,000/mm3 Platelet count at least 100,000/mm3 No
hemorrhagic events within the past 6 months Hepatic: Bilirubin normal SGOT normal INR no
greater than 1.5 Renal: Creatinine no greater than 1.5 times upper limit of normal
Cardiovascular: No thromboembolic events within the past 6 months Pulmonary: No evidence
of pneumonia Other: No known hypersensitivity to recombinant humanized murine monoclonal
antibodies No evidence of significant active infection (e.g., peritonitis or wound
abscess) Not pregnant or nursing Negative pregnancy test Fertile patients must use
effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent sargramostim (GM-CSF)
Chemotherapy: At least 12 months since prior fluorouracil-based adjuvant chemotherapy No
prior adjuvant irinotecan Endocrine therapy: Not specified Radiotherapy: See Disease
Characteristics At least 2 weeks since prior radiotherapy and recovered Surgery: See
Disease Characteristics Other: No prior therapy for advanced disease No concurrent
therapeutic anticoagulation except for low-dose coumadin for maintenance of indwelling
catheters