Carboplatin, Temozolomide, and Filgrastim in Treating Patients With Newly Diagnosed or Recurrent High-Grade Glioma

DISEASE CHARACTERISTICS: Histologically confirmed newly diagnosed glioblastoma multiforme or anaplastic astrocytoma Residual tumor on postoperative MRI Bidimensionally measurable disease PATIENT CHARACTERISTICS: Age: Under 65 Performance status: Karnofsky or Lansky 70-100% OR ECOG 0-2 Life expectancy: Not specified Hematopoietic: Absolute neutrophil count at least 1,000/mm^3 Hemoglobin at least 8 g/dL (transfusion allowed) Platelet count greater than 100,000/mm^3 Hepatic: Bilirubin less than 1.5 times upper limit of normal (ULN) SGPT no greater than 3 times ULN Renal: Age 5 years and under: Creatinine less than 1.2 mg/dL Age over 5 to 10 years: Creatinine less than 1.5 mg/dL Age over 10 to 15 years: Creatinine less than 1.8 mg/dL Age over 15 years: Creatinine less than 2.4 mg/dL Cardiovascular: No myocardial infarction within the past 6 months Other: No other concurrent serious medical condition that would preclude study Able to tolerate oral medications No prior malignancy for which patient received prior chemotherapy or spinal irradiation No history of severe allergic reaction to platinum-containing compounds Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: At least 72 hours since prior filgrastim (G-CSF) Chemotherapy: No prior chemotherapy No other concurrent chemotherapy Endocrine therapy: Concurrent steroids for tumor-related cerebral edema allowed No concurrent corticosteroids for solely antiemetic purposes Radiotherapy: No prior or concurrent radiotherapy Surgery: Recovered from prior surgery No concurrent surgery