OUTLINE: This is a nonrandomized study. Patients receive irinotecan (CPT-11) by IV over 90 minutes every 3 weeks. Dosage modifications are made based on toxicity. Retreatment may be delayed another 3 weeks (for a total of 6 weeks) to allow for recovery from toxic effects. Patient is taken off study if they do not recover from toxic effects, unless cause is documented to be unrelated to CPT-11. Patients with stable disease or partial response continue on treatment until disease progression or intolerable toxicity. Patients with complete response continue on treatment for another 2 courses and then are observed. Patients are followed every 3 months for 3 years or until disease progression.