PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior topotecan or ifosfamide At least 4 weeks since myelosuppressive chemotherapy At least 6 weeks since nitrosourea or mitomycin Must have recovered from prior therapy Endocrine therapy: Not specified Radiotherapy: No prior radiation therapy to pelvis At least 4 weeks since radiation therapy to major bone marrow containing areas Surgery: Must not have an option of surgery for this disease