Inclusion Criteria

DISEASE CHARACTERISTICS: Histologically proven oligodendroglioma or oligoastrocytoma (with
at least 25% oligodendroglial elements) Recurrent or progressive disease following both
radiotherapy and procarbazine/lomustine/vincristine chemotherapy (or other
nitrosoureas-based chemotherapy) Contrast enhancing, measurable disease (at least one
lesion measuring at least 1 cm) by CT or MRI required Within 2 weeks prior to study
treatment Within 3 days following concurrent surgery for the recurrence Steroid doses
stable or decreasing for at least 2 weeks prior to scan No extracranial disease

PATIENT CHARACTERISTICS: Age: 18-69 Performance status: WHO 0-2 Life expectancy: At least
3 months Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count at
least 100,000/mm3 Hepatic: Bilirubin no greater than 1.25 times upper limit of normal
(ULN) Alkaline phosphatase no greater than 2 times ULN AST/ALT no greater than 2 times ULN
Renal: Creatinine no greater than 1.25 times ULN Creatinine clearance at least 60 mL/min
Other: Not pregnant or lactating Effective contraception required of fertile women No
diseases interfering with follow-up

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: See Disease
Characteristics No more than one prior chemotherapy regimen At least 4 weeks since prior
chemotherapy Prior nitrosourea required At least 6 weeks since nitrosourea Endocrine
therapy: Not specified Radiotherapy: See Disease Characteristics More than 3 months since
radiotherapy Surgery: Not specified Other: No concurrent treatment with other
investigational agents or other antitumor agents