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