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