N. Fukumitsu1, K. Iwashita2, Y. Demizu3, T. Suzuki1, D. Hasegawa4, Y. Kosaka4, A. Kawamura4, and T. Soejima1; 1Kobe Proton Center, Kobe, Japan, 2Kobe Minimally invasive Cancer Center, Kobe, Japan, 3Hyogo Ion Beam Medical Center, Hyogo, Japan, 4Hyogo Prefectual Kobe Children’s Hospital, Kobe, Japan
Purpose/Objective(s): To compare craniospinal irradiation (CSI) of proton beam therapy (PBT) by irradiation methods and investigate the initial effect. Materials/
Methods: Twenty-four pediatric patients (age: 1–24 years) who received proton CSI were examined. Treatment method was passive scattered PBT (PSPT) in 8 patients and intensity modulated PBT (IMPT) in 16 patients. The whole vertebral body (WVB) technique was used for the 13 patients whose age was younger than 10 and vertebral body sparing (VBS) technique was used for the remaining 11 patients aged 10 and above. Follow up period was 17–44 (median 27) months. Doses of organs at risk, clinical target volume (CTV) and clinical data were examined. Results: The maximum dose of the lens in the IMPT was lower than PSPT (p=0.008). The mean dose of thyroid gland, lungs, esophagus and kidneys were lower in the patients treated by VBS than MVB technique (p<0.001, all). The minimum CTV dose of IMPT was higher than PSPT (p=0.01). Inhomogeneity index of IMPT was lower than PSPT (p=0.004). Blood cell counts were mildly decreased overall and white blood cell and red blood cell counts were reduced in WVB technique (p=0.02 and 0.04). Seven of 8 patients who were treated with PSPT and all 16 patients treated with IMPT have been still alive as of Dec 2022. Conclusion: IMPT can decrease the dose of lens than PSPT. VBS technique can decrease the doses of neck-chest-abdomen organs. The CTV coverage of IMPT are superior to PSPT. Hematological toxicity is mild.
.jpg "Nobuyoshi Fukumitsu, MD, PhD photo")