Part I: Patients receive cyclosporine IV over 6 hours and irinotecan IV over 90 minutes weekly for 4 weeks. Courses repeat every 6 weeks in the absence of unacceptable toxicity or disease progression. Cohorts of 3-12 patients receive escalating doses of irinotecan until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose at which at least one third of patients experience dose limiting toxicity (DLT).