DISEASE CHARACTERISTICS: Histologically proven refractory or recurrent supratentorial glioblastoma multiforme Bidimensionally measurable, enhancing residual disease by T1-weighted gadolinium-enhanced MRI required within 15 days prior to treatment Stable dose of corticosteroids required for at least 7 days prior to scan

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 60-100% Life expectancy: Not specified Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count at least 75,000/mm3 Hemoglobin at least 9 g/dL without blood transfusions for 15 days prior to treatment Hepatic: AST/SGOT no greater than 3 times upper limit of normal (ULN) Bilirubin less than 1.5 times ULN Renal: Creatinine no greater than 2 mg/dL OR Creatinine clearance at least 40 mL/min Other: Not allergic to etoposide Effective contraception required of fertile patients Negative serum pregnancy test required of fertile women No other acute or chronic medical or psychiatric condition

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior leflunomide (SU101) therapy No more than one prior single-agent or combination systemic chemotherapy regimen for initial disease Radiosensitizer(s) concurrent with radiotherapy allowed in addition to chemotherapy for primary disease At least 6 weeks since nitrosourea or mitomycin At least 2 weeks since vincristine No prior single-agent procarbazine At least 4 weeks since other chemotherapy No concurrent chemotherapy agents Endocrine therapy: No concurrent hormone therapy (except medroxyprogesterone acetate for appetite stimulation) Less than 4 weeks of prior hormonal therapy (tamoxifen or retinoids) if failed one prior chemotherapy regimen Radiotherapy: Prior conventional radiotherapy for initial disease required No more than one prior course of radiotherapy At least 8 weeks since radiotherapy No prior interstitial radiotherapy No concurrent radiotherapy Surgery: Maximally feasible resection for initial disease required No more than two resections permitted At least 1 week since surgery and/or biopsy for disease No prior interstitial radiotherapy or implanted BCNU-wafers No concurrent surgery (including resection, stereotactic surgery or interstitial implants) Other: No concurrent investigational agent At least 4 weeks since prior investigational agent At least 1 week since cholestyramine or monoamine oxidase inhibitors