OBJECTIVES: I. Compare the incidence of grade 2-4 diarrhea after completion of irinotecan in patients with metastatic colorectal cancer treated with octreotide vs placebo. II. Compare the duration of diarrhea and need for irinotecan dose reduction/ delay and hospitalization in patients treated with these 2 regimens. III. Collect data on tumor response and 1 year survival in patients treated with these 2 regimens. IV. Determine the pharmacokinetics and interaction of irinotecan and octreotide in a subset of these patients.