DISEASE CHARACTERISTICS:

• One of the following:

  • Histologically confirmed high-grade glioma

    • Glioblastoma multiforme
    • Gliosarcoma
    • Anaplastic astrocytoma
    • Anaplastic oligodendroglioma
    • Anaplastic mixed oligoastrocytoma
    • Malignant glioma/astrocytoma, not otherwise specified
    • Meningioma
    • Hemangioblastoma
    • Ependymoma
    • Primitive neuroectodermal tumors
    • Hemangiopericytoma
    • Progressive glioma
  • Clinically and radiographically diagnosed brain stem glioma

• Progressive or recurrent disease as determined by CT scan or MRI

  • Biopsy allowed for prior recent (i.e., within the past 12 weeks) resection of recurrent or progressive tumor
• Must have failed prior radiotherapy

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• Karnofsky 60-100%

Life expectancy:

• More than 8 weeks

Hematopoietic:

• WBC at least 2,300/mm^3
• Platelet count at least 90,000/mm^3
• Hemoglobin at least 8 g/dL (transfusions allowed)

Hepatic:

• Bilirubin less than 3 times upper limit of normal (ULN)
• SGOT less than 3 times ULN
• No significant active hepatic disease

Renal:

• Creatinine less than 2.0 mg/dL OR
• Creatinine clearance at least 60 mL/min
• No significant active renal disease

Cardiovascular:

• No significant active cardiac disease

Other:

• No other malignancy within the past 3 years except nonmelanoma skin cancer or carcinoma in situ of the cervix
• No significant active psychiatric disease
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for 2 months after study

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• At least 2 weeks since prior interferon
• No concurrent immunotherapy

Chemotherapy:

• At least 6 weeks since prior nitrosoureas
• At least 4 weeks since prior temozolomide or carboplatin
• At least 3 weeks since prior procarbazine
• At least 2 weeks since prior vincristine
• At least 4 weeks since other prior cytotoxic chemotherapy
• No concurrent chemotherapy

Endocrine therapy:

• At least 2 weeks since prior tamoxifen
• Concurrent steroids allowed for control of the signs and symptoms of increased intracranial pressure if on a stable dose for at least the past 5 days

Radiotherapy:

• See Disease Characteristics
• At least 2 weeks since prior radiotherapy
• No concurrent radiotherapy

Surgery:

• See Disease Characteristics
• At least 2 weeks since prior tumor resection

Other:

• At least 2 weeks since other prior noncytotoxic agents
• Concurrent enzyme-inducing antiepileptic drugs allowed
• No concurrent rifampin
• No concurrent grapefruit juice
• No other concurrent investigational agents