Purpose

RATIONALE: In this study a combination of anti-cancer drugs (chemotherapy) is used to treat brain tumors in young children. Using chemotherapy gives the brain more time to develop before radiation is given. The chemotherapy in this study includes the drug methotrexate. This drug was an important part of the two clinical trials which resulted in the best survival results for children less than 3 years of age with medulloblastoma. Most patients treated on this trial will also receive radiation which is carefully targeted to the area of the tumor. This type of radiation (focal conformal or proton beam radiotherapy) may result in fewer problems with thinking and learning than radiation to the whole brain and spinal cord. PURPOSE: This clinical trial is studying how well giving combination chemotherapy together with radiation therapy works in treating young patients with newly diagnosed central nervous system tumors.