S1718
Physics - Dose prediction/calculation, optimisation and applications for particle therapy planning
ESTRO 2026
therapy (PT) the preferred external radiotherapy modality for paediatric patients, and especially relevant for craniospinal irradiation (CSI) which is recommended for many indications. This study aims to estimate the risk of long-term effects in paediatric patients after PT CSI based on a methodology for individual assessment of the cumulative equivalent
doses at voxel level Material/Methods: A 5-year-old patient previously treated for
medulloblastoma was selected for this study. The PT treatment consisted of two plans: one delivering 36 Gy to the craniospinal volume, followed by a boost of 19.8 Gy to the surgical bed in the posterior fossa. The entire treatment plan was simulated using the MCNP6.2 code for an IBA Proteus proton therapy system. Calculations were performed on a voxelized phantom generated from the patient’s CT images. The neutron dose equivalent at voxel level was added to the weighted proton dose to obtain the accumulated dose (in Sv), following a previously introduced methodology [1]. This dose was used to estimate the risk of long-term effects, using models from PENTEC [2] and BEIR-VII [3] reports, and the Schneider model [4]. Results: Accumulated doses ranged from 41 Sv in the whole brain to 0.14 Sv in the gall bladder. The heart received approximately 3 Sv, corresponding to an estimated 1% risk of cardiac diseases. The estimated risk of cataract formation varied widely—from around 6% to as high as 60%—depending on the model applied. The lungs received a mean dose of 6.7 Sv, which is expected to represent a low risk of pulmonary complications, while the lifetime attributable risk of developing a second cancer could be as high as 20% if using BEIR model. Conclusion: Incorporating risk models into the treatment planning process might allow accounting for and mitigating potential long-term side effects. This study shows how individualised assessment of the total cumulative equivalent dose, together with the incorporation of risk models, allows the probability of long-term side effects to be estimated. The results emphasise the importance of the evaluation and recording of the total accumulated dose and the need of reliable dose- response models. References: 1. Romero-Expósito et al. Phys Med 129:104879;2025.2. Constine et al. Int J Radiat Oncol Biol Phys 119:316-320;2024. 3. National Research Council (NRC). Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2. 2006.4. Schneider et al. Theor Biol Med Model 8:27; 2011. Keywords: proton craniospinal irradiation, long-term effects
Digital Poster 1506
Risk of long-term side effects after a proton craniospinal treatment in paediatric patients. Maite Romero-Expósito 1,2 , Xavier Maldonado-Pijoan 3 , Mónica Ramos-Albiac 3 , Soraya Mico-Milla 3 , Alexandru Dasu 2,4 , Iuliana Toma-Dasu 5 , Mercè Beltrán-Vilagrasa 6 1 Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden. 2 -, Skandion Clinic, Uppsala, Sweden. 3 Servei d’Oncologia Radioteràpica., Hospital Universitari Vall d’Hebron, Barcelona, Spain. 4 Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden. 5 Department of Physics, Stockholm University, Stockholm, Sweden. 6 Servei de Física i Protecció Radiològica, Hospital Universitari Vall d’Hebron, Barcelona, Spain Purpose/Objective: Advances in oncological treatments have extended patients’ life expectancy, making long-term side effects increasingly relevant, particularly in children. Some of these effects can be life-threatening (e.g. second cancers) or can significantly impair quality-of-life (e.g. cataracts). The dosimetric properties of proton beams enable a substantial reduction of the integral dose to surrounding healthy tissues, which makes proton
Made with FlippingBook - Share PDF online