This study evaluated the hematological toxicity of 20 pediatric patients with high-risk medulloblastoma and other rare embryonal brain tumors treated with proton CSI. No serious hematological toxicity was observed, therefore no treatment delayed or discontinued. Leucocytes and neutrophils decreased at the beginning of treatment, but completely recovered at the end of treatment. The authors concluded that CSI with PT was proven to be safe in this setting of pediatric patients.