PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: At least 6 weeks since prior adjuvant chemotherapy for brain tumor No other prior chemotherapy Endocrine therapy: Must be on stable or decreasing doses of corticosteroids for at least 2 weeks Radiotherapy: At least 3 months since prior radiotherapy to the brain No prior high dose radiotherapy No prior stereotactic boost or implant radiotherapy Surgery: No prior surgery (except biopsy) for recurrent brain tumor At least 3 months since prior surgery for primary brain tumor Other: No other concurrent anticancer agents No other concurrent investigational therapy