PRIOR CONCURRENT THERAPY: Biologic therapy: At least 2 weeks since prior immunotherapy and recovered No concurrent filgrastim (G-CSF) No concurrent immunotherapy Chemotherapy: See Disease Characteristics No prior nitrocamptothecin, irinotecan, or other camptothecin analog At least 2 weeks since other prior chemotherapy and recovered No other concurrent chemotherapy Endocrine therapy: No concurrent anticancer hormonal therapy Radiotherapy: See Disease Characteristics At least 2 weeks since prior radiotherapy and recovered No concurrent radiotherapy Surgery: At least 2 weeks since prior surgery and recovered No scheduled major surgery within 8 weeks following initiation of treatment