OUTLINE: This is a randomized, double blind, placebo controlled, multicenter study. Patients are stratified according to prior pelvic irradiation (yes vs no), age (under 70 vs 70 and over), and ECOG performance status (0 vs 1 or 2). Patients are randomized to 1 of 2 treatment arms. Arm I: Patients receive octreotide intramuscularly (IM) once. Beginning 10-14 days later, patients receive irinotecan IV over 90 minutes on day 1. Patients also receive octreotide IM on the same day as irinotecan. Arm II: Patients receive placebo IM once. Beginning 10-14 days later, patients receive irinotecan as in arm I. Patients also receive placebo IM on the same day as irinotecan. Therapy continues every 3 weeks for at least 6 courses in the absence of disease progression or unacceptable toxicity. Patients are followed every 3 months through year 1.