DISEASE CHARACTERISTICS:

• Stratum I:

  • Newly diagnosed diffuse intrinsic brainstem malignant glioma
  • No disseminated disease
  • No radiographic evidence of intratumoral hemorrhage before or after radiotherapy

• Stratum II (A- no concurrent enzyme-inducing anticonvulsant drugs [EIACDs] vs B-concurrent use of EIACDs [closed to accrual as of 5/10/04]):

  • Histologically confirmed recurrent or refractory anaplastic astrocytoma, glioblastoma multiforme, or other high-grade glioma (including recurrent brain stem glioma
  • No intratumoral hemorrhage unrelated to prior surgical procedure

PATIENT CHARACTERISTICS:

Age:

• 3 to 21

Performance status:

• Karnofsky 50-100% OR
• Lansky 50-100%

Life expectancy:

• Not specified

Hematopoietic:

• Absolute neutrophil count greater than 1,000/mm^3
• Platelet count greater than 100,000/mm^3 (transfusion independent)
• Hemoglobin greater than 8 g/dL (transfusion allowed)

Hepatic:

• Bilirubin no greater than 1.5 times normal for age
• SGPT less than 3 times normal for age
• Albumin at least 2 g/dL
• No significant hepatic disease

Renal:

• Creatinine less than 1.5 times normal for age OR
• Glomerular filtration rate greater than 70 mL/min
• No significant renal disease

Cardiovascular:

• No significant cardiac disease
• No deep venous or arterial thrombosis within the past 6 weeks

Pulmonary:

• No significant pulmonary disease

Other:

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective barrier contraception during and for 6 months after study participation
• No uncontrolled infection
• No significant gastrointestinal disease
• No significant psychiatric disease
• Neurological deficits allowed if stable for at least 1 week prior to study (stratum II)

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• More than 2 weeks since prior colony-stimulating growth factors (e.g., filgrastim [G-CSF], sargramostim [GM-CSF], or epoetin alfa)
• At least 3 months since prior bone marrow transplantation (stratum II)

Chemotherapy:

• No prior chemotherapy (stratum I)
• At least 3 weeks since prior myelosuppressive chemotherapy (6 weeks for nitrosoureas) and recovered (stratum II)

Endocrine therapy:

• Prior routine corticosteroids allowed
• Concurrent corticosteroids allowed if on stable or decreasing dose for at least 1 week prior to study

Radiotherapy:

• Stratum I:

  • No prior radiotherapy

• Stratum II:

  • At least 3 months since prior craniospinal radiotherapy (18 Gy or more)
  • At least 8 weeks since prior local radiotherapy to primary tumor
  • At least 2 weeks since prior focal radiotherapy for symptomatic metastases

Surgery:

• See Disease Characteristics

Other:

• No prior imatinib mesylate (stratum II)
• At least 2 weeks since beginning or discontinuing medications affecting cytochrome P450 3A4, 5, and 7 isoenzyme metabolism
• No other concurrent anticancer drug
• No other concurrent experimental drug
• No concurrent warfarin
• No concurrent enzyme-inducing anticonvulsant drugs (stratum I)