PRIOR CONCURRENT THERAPY: Biologic therapy: At least 3 weeks since prior biologic therapy Chemotherapy: At least 3 weeks since prior chemotherapy and recovered No prior topotecan or camptothecin therapy No more than 1 prior chemotherapy regimen (either single or combination chemotherapy) Endocrine therapy: At least 3 weeks since prior endocrine therapy Radiotherapy: At least 3 weeks since prior radiotherapy and recovered Surgery: Prior surgery allowed and recovered