Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed central nervous system cancer including:

- Medulloblastoma with either local residual disease of greater than 1 cm^2 on MRI
following resection or evidence of metastases (M1-4)

- Other primitive neuroectodermal tumors

- Ependymoma with evidence of subarachnoid metastases

- Must have less than 1 cm of midline shift or no acute elevated intercranial pressure

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Performance status:

- ECOG 0-2

Life expectancy:

- Not specified

Hematopoietic:

- WBC greater than 4,000/mm^3

- Platelet count greater than 125,000/mm^3

- Hemoglobin greater than 10 g/dL

- No preexisting hematologic condition that would increase toxicity or limit ability to
comply with evaluations and follow-up

Hepatic:

- Bilirubin less than 2 times upper limit of normal (ULN)

- SGOT less than 2 times ULN

- Alkaline phosphatase less than 2 times ULN

- No preexisting hepatic condition that would increase toxicity or limit ability to
comply with evaluations and follow-up

Renal:

- Creatinine greater than 70 mL/min

- No preexisting renal condition that would increase toxicity or limit ability to
comply with evaluations and follow-up

Pulmonary:

- No history of significant pulmonary disease or, if there is preexisting pulmonary
disease, then DLCO greater than 60% of predicted

- No preexisting pulmonary condition that would increase toxicity or limit ability to
comply with evaluations and follow-up

Other:

- No preexisting psychiatric condition that would increase toxicity or limit ability to
comply with evaluations and follow-up

- No prior or concurrent malignancies within the past 5 years except curatively treated
carcinoma in situ of the cervix or basal cell or squamous cell skin cancer

- Not pregnant or nursing

- Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- Not specified

Chemotherapy:

- No prior chemotherapy

Endocrine therapy:

- No increasing doses of steroids for intracranial disease within 3 days of
registration

Radiotherapy:

- No prior radiotherapy

Surgery:

- 10-28 days since prior surgical resection OR

- At least 5 days since prior biopsy