Proton Craniospinal Irradiation With Bone Sparing to Decrease Growth Decrement From Radiation

Inclusion Criteria: * Age ≥ 3 years and ≤ 18 years at the time of registration * Histologically proven malignancy necessitating cranio-spinal irradiation. This will include patients with a diagnosis of medulloblastoma, Supratentorial primitive neuroectodermal tumor (SPNET), germ cell tumor (GCT), disseminated ependymoma, embryonal tumor with abundant neuropil and true rosettes (ETANTR), Atypical Teratoid/Rhabdoid Tumor (ATRT), and disseminated low-grade glioma (LGG). * Life expectancy ≥ 12 months. * Signed informed consent document and assent when appropriate. * HGB of \> 10 g/L and PLT count \> 80 K/uL Exclusion Criteria: * Any prior therapeutic radiation therapy \> 500 cGy has been delivered. * Individuals with a history of a different malignancy are ineligible except for the following circumstances: if they have been disease-free for at least 5 years and are deemed by the investigator to be a low-risk for recurrence of that malignancy; or, have had only cervical cancer in situ, or basal cell or squamous cell carcinoma of the skin. * Any major uncontrolled or poorly controlled intercurrent illness that would limit compliance with study requirements. * Pregnant females are excluded. Females of childbearing age/menstruating must confirm that either they are not sexually active or have a negative pregnancy test prior to initiation of radiation therapy. * Patients that receive concurrent chemotherapy with the exception of concurrent Vincristine.