OUTLINE: This is a dose escalation study. Patients receive mitomycin IV over 20 to 30 minutes on day 1 and irinotecan IV over 90 minutes on days 2, 8, 15, and 22, followed by 2 weeks of rest beginning on day 29. Treatment continues every 6 weeks in the absence of disease progression or unacceptable toxicity. Cohorts of 3 to 6 patients each receive escalating doses of mitomycin and irinotecan until the maximum tolerated dose (MTD) is reached. The MTD is defined as the dose at which no more than 1 of 6 patients experiences dose limiting toxicity. Patients are followed for 1 month.