A study by the Samsung Medical Center group, Korea. In this study 66 pediatric brain tumor patients who received either proton beam craniospinal irradiation (PrCSI) (n=36) or photon beam craniospinal irradiation (PhCSI) (n=30) were reviewed, and the early hematological changes in hemoglobin levels, absolute lymphocyte counts, and platelet counts, as well as acute toxicities were compared up to 4 weeks after the completion of radiotherapy. This study found no significant differences in hemoglobin levels between the two groups at any timepoint, but absolute lymphocyte counts and platelet counts were significantly lower in the PhCSI group than in PrCSI group at every timepoint. This study demonstrated that PrCSI resulted in a significantly lower rate of decline and better recovery of absolute lymphocyte and platelet counts. The rate of grade 3 acute anemia was significantly lower in the PrCSI group than in in the PhCSI group.