OUTLINE: This is a randomized, open-label, multicenter study. Patients are stratified according to measurable disease (yes vs no), Karnofsky performance status (50-70% vs 70-100%), and prior radiotherapy. Patients are randomized to 1 of 2 treatment arms. Arm I: Patients receive oral nitrocamptothecin on days 1-5. Treatment repeats every week for 8 courses in the absence of disease progression or unacceptable toxicity. Patients with stable or responding disease after week 8 may receive additional courses. Arm II: Patients receive gemcitabine IV over 30 minutes on day 1. Treatment repeats every week for 7 courses in the absence of disease progression or unacceptable toxicity. Patients then undergo 1 week of rest. Patients with stable or responding disease after week 8 may receive gemcitabine IV over 30 minutes on days 1, 8, and 15. Courses repeat every 4 weeks. Pain is assessed within 7 days prior to study, at days 28 and 56 during study, and then every 28 days after completion of study. Patients are followed every 3 months for 1 year or until death.