ESTRO 2025 - Abstract Book

S1623

Clinical – äediatric tumours

ESTRO 2025

Sweden. 5 Department of Oncology, and Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden. 6 Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden. 7 Department of Radiation Sciences, Oncology, Umeå University, Umeå, Sweden. 8 Department of Oncology, Skåne University Hospital, Lund, Sweden Purpose/Objective: Neuroblastoma is one of the most common types of solid tumours in children with about 20 new cases in Sweden each year. All paediatric radiotherapy centres in Sweden have access to proton radiotherapy and patients considered for proton radiotherapy will have comparative photon and proton treatment plans made. The aim of this study is to analyse doses to organs at risk in comparative photon and proton treatment plans for children treated for neuroblastoma. Material/Methods: All children in Sweden treated with curative intent radiotherapy for neuroblastoma in the abdomen during 2017 2024 with comparative photon and proton treatment plans were included. The patients were identified through a national registry (RADTOX), and data on doses to relevant structures were extracted from the treatment planning system. Doses to organs at risk were compared in each individual patient’s clinical photon and proton treatment plan and differences were tested through Wilcoxon signed-rank test. Integral dose was defined as the percentage of the scanned body that received ≥5 Gy (Body V5%) and ≥10 Gy (Body V10%). Results: 30 patients with comparative photon and proton treatment plans were included. Fifteen (50%) females and 15 (50%) males. The median age was 45 months (range 11-150). The majority (90%) were treated with 21 Gy and the remainder (10%) with 36 Gy. The integral dose was significantly lower in the proton treatment plans compared to the photon treatment plans measured as both Body V5%, p = <0.001 and Body V10%, p = <0.001 (Figure 1). There was no significant difference in conformity index (volume that have received 95% of prescribed dose divided by CTV volume) comparing the photon and proton treatment plans. The mean dose to the kidneys was significantly lower in the proton treatment plans (Md = 5.63 Gy, IQR 2.47-13.08 Gy) compared to the photon treatment plans (Md = 7.98 Gy, IQR 2.96-13.11 Gy), p = 0.045, and furthermore, the mean dose to the liver was significantly lower in the proton treatment plans (Md = 2.74 Gy, IQR 1.35-4.35 Gy) compared to the photon treatment plans (Md= 7.54 Gy, IQR 5.65-9.39 Gy), p < 0.001.

Figure 1.