Proton Beam Radiation Therapy in Treating Young Patients Who Have Undergone Biopsy or Surgery for Medulloblastoma or Pineoblastoma

RATIONALE: Specialized radiation therapy that delivers radiation directly to the area where a tumor was surgically removed may kill any remaining tumor cells and cause less damage to normal tissue. PURPOSE: This phase II trial is studying how well proton beam radiation therapy works in treating young patients who have undergone biopsy or surgery for medulloblastoma or pineoblastoma.