There are two types of external radiation treatments (proton beam and photon beam). As part of the participant's treatment, they will receive radiation to the entire central nervous system (CNS); this is known as craniospinal irradiation (CSI). In the past, photon radiation therapy has been used for CSI. In this study we will be examining the effects of proton beam radiation therapy. Studies have suggested that this kind of radiation can cause less damage to normal tissue than photon radiation therapy. The physical characteristics of proton beam radiation let the doctor safely deliver the amount of radiation delivered to the tumor that is normally delivered through standard therapy but spare more normal tissue in the process.

• Before beginning radiation therapy, participants will have scans done in order to prepare for the radiation treatment. Doctors will use information gathered from these scans to plan the best way to deliver radiation to the tumor.
• The following procedures will be performed either before or during the radiotherapy: Hearing exam; neurocognitive exam; blood tests and cerebral spinal fluid test.
• Not everyone who participates in this study will receive the same amount of proton radiation therapy. The length of time and amount of radiation received will depend upon the condition of the participant's disease. Radiation treatment will be given once a day, 5 days a week (Monday-Friday). The overall treatment course will be approximately 6 weeks.

Inclusion Criteria:

• Participants must have undergone biopsy or attempted surgical resection and must have histologically confirmed medulloblastoma or pineoblastoma.
• Participants may have had a gross total resection, sub-total resection or biopsy only.
• For patients with no prior chemotherapy, treatment must start within 35 days of definitive surgery or as indicated if enrolled on therapeutic study
• Age range between 3 and 25 at the time of enrollment
• Life expectancy of greater than 3 months
• Blood laboratory values as outlined in the protocol
• Women of child-bearing potential and men must agree to use adequate contraception prior to study entry and for the duration of study participation

Exclusion Criteria:

• Patients with more than one previous chemotherapy regimen
• Patients with recurrent or progressive disease after one or more regimens of pre-radiation chemotherapy
• Patients with prior radiation therapy
• Any major uncontrolled or poorly controlled intercurrent illness that would limit compliance with study requirements
• Pregnant women

Through start of radiotherapy treatment to study end (up to 5 years post radiation treatment)

All adverse events experienced by participants will be collected from the time of the first dose of study treatment, through the study and until the final study visit. All patients were assessed for acute toxicity on a weekly basis during CSI. Grading of acute toxicity was done per the CTEP (Cancer Therapy Evaluation Program) Active Version of CTCAE (Common Terminology Criteria for Adverse Events).