OUTLINE: This is a dose escalation study. Patients receive oral irinotecan once daily for 14 days. Courses repeat every 3 weeks in the absence of disease progression or unacceptable toxicity. Cohorts of 3-6 patients receive escalating doses of irinotecan until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 or more of 6 patients experience dose limiting toxicity. Patients are followed monthly for 6 months.