DISEASE CHARACTERISTICS: Histologically or cytologically confirmed stage IV colorectal cancer Measurable disease defined as lesions that measure at least 20 mm in one dimension using conventional techniques or at least 10 mm with spiral CT scan not including: Bone lesions Leptomeningeal disease Ascites Pleural/pericardial effusion Inflammatory breast disease Lymphangitis cutis/pulmonis Abdominal masses that are not confirmed and followed by imaging techniques Cystic lesions Recurrent disease allowed after adjuvant chemotherapy if recurrence occurred at least 6 months after completion of therapy No known brain metastases