Inclusion Criteria

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