DISEASE CHARACTERISTICS: Histologically or cytologically confirmed cancer of the colon or rectum that is locally advanced or metastatic Primary lesion was or is located in the large bowel as confirmed by endoscopy, radiology, or surgery Radiologic or clinical evidence of metastasis subsequent to resection does not require histologic or cytologic confirmation unless: Interval between primary surgery and development of metastasis is greater than 5 years OR Primary cancer was Dukes' A or B1 Ineligible for potentially curative therapy, e.g.: Surgical resection of a limited hepatic or pulmonary metastasis Irradiation of locally recurrent colon or rectal cancer No or minimal symptoms related to the cancer, i.e.: No persistent pain requiring regular narcotic analgesia No persistent fever greater than 38 degrees C No symptomatic bowel obstruction No persistent nausea requiring medication No weight loss of greater than 5 kg over the previous 3 months unless clearly not associated with the cancer (e.g., associated with surgery or intercurrent illness) Symptomatic relapse/metastases rendered asymptomatic by secondary surgery or radiotherapy are eligible provided the patient remains asymptomatic for at least 6 weeks following such treatment No CNS metastases No significant ascites, pleural effusion, or pericardial effusion