ESTRO 2025 - Abstract Book

S3485

Physics - Optimisation, algorithms and applications for ion beam treatment planning

ESTRO 2025

Keywords: FLASH, robustness, proton therapy

References: [1] Folkerts, M. M. et al. (2020). A framework for defining FLASH dose rate for pencil beam scanning. Medical physics , 47 (12), 6396-6404. [2] Santo, R. J. et al. (2023). Pencil-beam delivery pattern optimization increases dose rate for stereotactic FLASH proton therapy. IJROBP , 115 (3), 759-767. [3] Sørensen, B. S. et al. (2024). Proton FLASH: impact of dose rate and split dose on acute skin toxicity in a murine model. IJROBP . [4] Unkelbach, J., & Paganetti, H. (2018, April). Robust proton treatment planning: physical and biological optimization. In Seminars in radiation oncology (Vol. 28, No. 2, pp. 88-96). WB Saunders.

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Digital Poster Validation of automated IMPT- and joint proton transmission beam-IMPT planning for nasopharyngeal cancer patients Merle Huiskes 1 , Wens Kong 2 , Sebastiaan Breedveld 2 , Koen Crama 1,3 , Steven Habraken 1,3 , Ben Heijmen 2 , Coen Rasch 1,3 , Eleftheria Astreinidou 1 1 Department of Radiation Oncology, Leiden University Medical Center, Leiden, Netherlands. 2 Department of Radiotherapy, Erasmus MC Cancer Institute, Rotterdam, Netherlands. 3 Radiation Oncology, HollandPTC, Delft, Netherlands Purpose/Objective: To compare automated intensity modulated proton therapy (autoIMPT) plans and automated joint transmission beam (TB) and IMPT plans (autoIMPT+TB), with manually created clinical IMPT plans, for nasopharyngeal cancer (NPC) patients. Material/Methods: Twenty-four NPC patients, previously treated with IMPT were included. Dose prescription was 7000 cGy (RBE) to the primary tumor (CTV7000) and 5425 cGy (RBE) to the bilateral elective nodal volumes (CTV5425). Manual and automated plans utilized the clinical six-beam configuration and were generated with scenario-based robust optimization (21 scenarios, 3 mm setup error and ±3% range uncertainty). Three of the 24 patients were used to develop a class solution and configure the Erasmus-iCycle automated planning approach, in line with the clinical planning requirements. Subsequently, robust IMPT- and IMPT+TB plans were automatically generated for 21 patients. Automatically generated plans were compared with the manual plans regarding (robust) target coverage, OAR doses and normal tissue complication probabilities (NTCP). Results: The voxel-wise minimum (vw-min) target D98% of the automated plans was similar and in some cases better that the clinical plans, especially for those clinical cases where the target coverage goal of D98%≥94% was compromised (Figure 1). Median D98% vw-min CTV7000 values were: 6892 cGy (clinical), 6585 cGy (autoIMPT), 6589 cGy (autoIMPT+TB) and for CTV5425: 5114 cGy (clinical), 5135 cGy (autoIMPT), 5129 cGy (autoIMPT+TB). Target coverage was not further enhanced with incorporation of TB to IMPT as compared to IMPT alone.