PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent immunotherapy Chemotherapy: No more than 4 courses of combination chemotherapy that included an alkylating agent, cisplatin, or carboplatin (applies once grade 1 or worse myelosuppression is reported on this study) No prior mitomycin or nitrosoureas At least 28 days since chemotherapy No concurrent chemotherapy Endocrine therapy: Not specified Radiotherapy: No prior radiotherapy to wide ports involving pelvis or 20% of bone marrow At least 28 days since large-field radiotherapy No concurrent radiotherapy Surgery: At least 14 days since major surgery Other: No bone marrow transplantation