OUTLINE: Patients receive a 90 minute continuous infusion of irinotecan on days 1, 8, 15, and 22 for 4 weeks, followed by a 2 week rest period. Courses of treatment are repeated every 42 days. Patients continue treatment in the absence of disease progression or unacceptable toxicity. Patients are followed every 3 months for 1 year, then every 6 months for the next 4 years.