Exclusion Criteria: Patients expressing tumor markers as their only evidence of disease or who have previously irradiated areas that have not increased in size; Prior chemotherapy treatment with irinotecan and mitomycin; Prior abdominal and/or pelvic radiation therapy; Current history of hepatitis B infection or positive test for hepatitis B surface antigen; Hepatic encephalopathy including somnolence, confusion, or asterixis; History of myocardial infarction within 6 months or history of congestive heart failure (CHF); clinical evidence of CHF; Evidence of arrhythmia in patients with history of cardiac arrhythmia; Uncontrolled hypertension, unstable angina, active CHF, or serious uncontrolled cardiac arrhythmia; Interstitial pneumonia or fibroid lung (patients must have large pleural effusions drained and sclerosed or controlled prior to study; patients must have clinically apparent ascites drained prior to irinotecan treatment); CNS metastases or carcinomatous meningitis; Concurrent use of anticonvulsants; Active or uncontrolled