The median percent change in weight at completion of radiation therapy (RT) for patients receiving proton craniospinal irradiation (p-CSI) was −1.2% (range +14 to −8.4%) compared to −5.8% for conventional photons (x-CSI; range +5.8 to −17.1%; p=0.004; panel a); One month after RT, the median percent change in weight +0.1% for p-CSI (range +14.6 to −14.2%) compared to −4.4% for x-CSI (range +12.2 to −23%; p=0.1; panel a). The median percentage of baseline white blood cells (WBC), hemoglobin and platelets at their nadir for patients receiving p-CSI (panel b: 55%, 97%, 65%, range 13–100%, 76–113%, 36–108%, respectively) compared to x-CSI (46%, 88%, 48%, range 25–84%, 71–100%, 5–78%; p=0.04, 0.009, 0.05, respectively); The median percentage of baseline WBCs, hemoglobin and platelets one month after RT (panel c; 78%, 105%, 87%, range 24–139%, 74–124%, 41–266%) compared to x-CSI (56%, 88%, 73%, range 18–146%, 68–106%, 17–158%; p=0.1, 0.002, and 0.1, respectively).