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.

Inclusion Criteria:

• The patient's legal guardian voluntarily signs the written informed consent form.
• Age at diagnosis > 3 years and ≤ 18 years.
• Histopathologically confirmed diagnosis of a central nervous system (CNS) tumor.
• Indication for craniospinal irradiation (CSI) confirmed by multidisciplinary team (MDT) discussion.
• Karnofsky Performance Score (KPS) ≥ 80.
• For postoperative patients, complete healing of the surgical incision with no evidence of wound infection or other complications.
• For women of childbearing potential, effective contraception must be used for at least one month prior to screening, and they must commit to continued contraception throughout the study period and for the required time after study completion.

Exclusion Criteria:

• Previous receipt of any form of spinal radiotherapy.
• Previous major spinal surgery for any reason.
• Presence of clinically significant and confirmed spinal deformity at enrollment (e.g., Cobb angle > 10° measured by MRI or X-ray).
• Presence of medical contraindications to proton radiotherapy.
• Presence of any severe, uncontrolled systemic disease (e.g., active infection, severe cardiac, hepatic, renal, or respiratory insufficiency) that, in the investigator's judgment, makes the subject unsuitable for treatment under this protocol.
• Female patients who are pregnant or breastfeeding.
• Presence of any severe cognitive or psychiatric disorder that prevents understanding of or cooperation with study assessments.

This is a prospective observational study enrolling 38 pediatric patients aged >3 years and ≤18 years with histologically confirmed central nervous system tumors requiring craniospinal irradiation (CSI). Patients will be assigned to 2 cohorts: low-dose CSI and high-dose CSI. All participants will receive vertebral body-sparing intensity-modulated proton therapy (IMPT) and standard chemotherapy according to clinical guidelines.