DISEASE CHARACTERISTICS:

• Histologically confirmed newly diagnosed malignant central nervous system tumor not requiring immediate radiotherapy
• Patients with diffuse pontine tumors do not require histological confirmation

• Eligible types include the following:

  • Ependymoma

  • Malignant glioma

    • Anaplastic astrocytoma
    • Glioblastoma multiforme
    • Anaplastic oligodendroglioma
    • Gliosarcoma
    • Anaplastic mixed oligoastrocytoma
  • Brainstem glioma
  • Primitive neuroectodermal tumor
  • Nongerminoma germ cell tumor

• At least one bidimensionally measurable lesion

  • At least 1.5 cm2 within 72 hours of surgical resection or greater than 14 days after surgery
  • Diffuse pontine tumors are not required to be measurable
• Neurologically stable

PATIENT CHARACTERISTICS:

Age:

• 4 to 21

Performance status:

• Karnofsky or Lansky 70-100%

Life expectancy:

• Greater than 12 weeks

Hematopoietic:

• Absolute neutrophil count at least 1,500/mm^3
• Platelet count at least 100,000/mm^3
• Hemoglobin at least 10 g/dL

Hepatic:

• Bilirubin less than 1.5 times upper limit of normal (ULN)
• Alkaline phosphatase less than 2 times ULN
• SGOT and SGPT less than 2.5 times ULN

Renal:

• BUN and creatinine less than 1.5 times ULN

Other:

• Must be able to swallow capsules
• No acute infection treated with intravenous antibiotics
• No nonmalignant systemic disease that makes patient a poor medical risk
• No frequent vomiting or medical condition that may interfere with oral medication intake (e.g., partial bowel obstruction)
• No other prior or concurrent malignancies except surgically cured carcinoma in situ of the cervix or basal or squamous cell carcinoma of the skin
• HIV negative
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• No more than one prior biologic therapy regimen
• No concurrent biologic therapy
• No concurrent growth factors or epoetin alfa

Chemotherapy:

• No more than one prior chemotherapy regimen
• No other concurrent chemotherapy

Endocrine therapy:

• No increasing doses of steroids within one week of study

Radiotherapy:

• See Disease Characteristics
• No concurrent radiotherapy

Surgery:

• At least 2 weeks, but no greater than 4 weeks, since prior surgical resection and recovered

Other:

• No other concurrent investigational drugs