OUTLINE: This is a dose escalation study. Patients are stratified according to prior pelvic radiation therapy (yes vs no). Patients with no prior pelvic radiation are further stratified according to AST, bilirubin, and creatinine levels. Patients receive irinotecan IV over 90 minutes every 3 weeks for a total of 2 courses. After patients are reevaluated, treatment may continue in the absence of disease progression or unacceptable toxicity. Cohorts of 3 to 6 patients receive escalating doses of irinotecan. Dose escalation proceeds within each stratum until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose below that at which 2 of 6 patients experience dose-limiting toxicity.