Chemotherapy in Treating Patients With Recurrent Malignant Glioma

DISEASE CHARACTERISTICS: Histologically proven recurrent primary malignant glioma Measurable recurrent or residual primary central nervous system neoplasm confirmed by MRI PATIENT CHARACTERISTICS: Age: 18 and over Performance Status: Karnofsky at least 60% Hematopoietic: Hematocrit greater than 29% ANC greater than 1,500/mm^3 Platelet count greater than 125,000/mm^3 Hepatic: SGOT less than 1.5 times upper limit of normal (ULN) Bilirubin less than 1.5 times ULN Renal: Creatinine less than 1.5 mg/dL BUN less than 25 mg/dL Other: Not pregnant Effective contraceptive method must be used for the duration of the study PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior chemotherapy within 6 weeks of study No prior topotecan or carmustine treatment failure No more than 1 prior chemotherapy regimen Endocrine therapy: Patients taking corticosteroids must be on stable dose for at least 2 weeks prior to study and the dose should not escalate over entry level Radiotherapy: No prior radiotherapy within 6 weeks of study Surgery: No prior surgical resection within 3 weeks of study Other: No concurrent medication that may interfere with study results