Comparison of Radiation Therapy Regimens in Combination With Chemotherapy in Treating Young Patients With Newly Diagnosed Standard-Risk Medulloblastoma

Inclusion Criteria:

* Histologically confirmed medulloblastoma located in the posterior fossa

  * Standard-risk disease
* Minimal volume, non-disseminated disease, defined by the following:

  * Residual tumor ≤ 1.5 cm\^2 confirmed by MRI with contrast imaging within 21 days after surgery
  * No metastatic disease in the head, spine, or cerebrospinal fluid (CSF) confirmed by both of the following:

    * Enhanced MRI of the spine within 5 days before surgery OR within 28 days after surgery
    * Negative cytological examination of CSF after surgery, but before study enrollment
* Brain stem involvement allowed
* Performance status - Karnofsky 50-100% (\> 16 years of age)
* Performance status - Lansky 30-100% (≤ 16 years of age)
* Absolute neutrophil count \> 1,500/uL
* Platelet count \> 100,000/uL (transfusion independent)
* Hemoglobin \> 10 g/dL (transfusions allowed)
* Bilirubin \< 1.5 times upper limit of normal (ULN) for age
* AST or ALT \< 1.5 times ULN for age
* Creatinine clearance OR radioisotope glomerular filtration rate \>= 70 mL/min/1.73m\^2 or a serum creatinine based on age/gender as follows:

Age Maximum Serum Creatine (mg/dL)

* 1month to \< 6 months male: 0.4 female: 0.4
* 6 months to \<1 year male: 0.5 female: 0.5
* 1 year to \< 2 years male: 0.6 female: 0.6
* 2 to \< 6 years male: 0.8 female: 0.8
* 6 to \< 10 years male: 1 female: 1
* 10 to \< 13 years male: 1.2 female: 1.2
* 13 to \< 16 years male: 1.5 female: 1.4
* \>= 16 years male: 1.7 female: 1.4

  * Not pregnant or nursing
  * Negative pregnancy test
  * Fertile patients must use effective contraception
  * No prior chemotherapy
  * Prior corticosteroids allowed
  * No prior radiotherapy