DISEASE CHARACTERISTICS:

• Histologically confirmed CNS tumors of any of the following :

  • Medulloblastoma (all histologic subtypes, including medullomyoblastoma and melanotic medulloblastoma)
  • Supratentorial primitive neuroectodermal tumor (PNET) (including CNS neuroblastoma or ganglioneuroblastoma, medulloepithelioma, and ependymoblastoma)
  • Pineoblastoma
  • Atypical teratoid rhabdoid tumor (ATRT)
  • Choroid plexus carcinoma
  • Ependymoma (< 12 months of age or metastatic disease at diagnosis)
  • Synchronous extraneural ATRT allowed

• Meets criteria for 1 of the following risk groups:

  • Low-risk group:

    • Histologically confirmed nodular desmoplastic medulloblastoma, including medulloblastoma with extensive nodularity

      • Focal areas of anaplasia or other atypical features suggesting more aggressive phenotype in a tumor otherwise considered nodular desmoplastic should be treated on the intermediate-risk group, with final risk stratification at the discretion of principal investigator and study pathologist

    • No evidence of CNS metastasis 7 to 28 days after surgery by MRI and cytologic examination of lumbar cerebrospinal fluid (CSF)

      • Ventricular CSF from a shunt or Ommaya reservoir may be used to rule out M1 disease when lumbar puncture is medically contraindicated
      • Intermediate-risk group assignment when there is no other evidence of metastasis and CSF sampling is not possible
    • Gross total resection, defined as residual tumor or imaging abnormality (not definitive for residual tumor) with a size of < 1 cm^2 confirmed on postoperative CT scan or MRI
    • Brain stem invasion by the tumor in the absence of imaging evidence of residual tumor (tumor size < 1 cm^2) and otherwise meets criteria for the low-risk group, the patient will be classified as low-risk

  • Intermediate-risk group:

    • Histologically confirmed nodular desmoplastic medulloblastoma with less than gross total resection and no evidence of metastasis
    • Any eligible histologic diagnosis other than desmoplastic medulloblastoma with no evidence of CNS metastasis

  • High-risk group:

    • Any eligible histologic diagnosis with evidence of CNS metastasis
    • Patients with extraneural metastasis are eligible for treatment on the high-risk group
• Newly diagnosed disease

PATIENT CHARACTERISTICS:

• Lansky performance status ≥ 30 (except for posterior fossa syndrome)
• WBC > 2,000/mm^3
• Platelets > 50,000/mm^3 (without support)
• Hemoglobin > 8 g/dL (with or without support)
• ANC > 500/mm^3
• Serum creatinine < 3 times upper limit of normal (ULN)
• ALT < 5 times ULN
• Total bilirubin < 3 times ULN

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• No more than 31 days since prior definitive surgery
• No prior radiotherapy or chemotherapy other than corticosteroid therapy