his is a single-center, prospective observational study in children and adolescents with central nervous system tumors who need whole-brain and whole-spine radiation therapy (craniospinal irradiation, CSI). The study uses proton therapy with a special vertebral body-sparing (VBS) technique to protect the front and center of the vertebrae, which helps preserve bone marrow function and growth. The main goals are to find safe dose limits for the vertebrae and check how often severe side effects occur. The study will also look at bone marrow preservation, spinal deformity, tumor control, survival, chemotherapy completion, neurocognitive function, quality of life, and growth and development for up to 5 years after treatment.