ESTRO 2025 - Abstract Book

S2391

Interdisciplinary – Other

ESTRO 2025

Conclusion The developed mathematical modeling methods can be used to guide new pre-clinical and clinical treatment protocols for individual tumor-immune contextures. Upon successful prospective verification, this can help advance personalized treatment for metastatic cancer patients on a patient-individual level.

Keywords: Metastasis, Abscopal Effect, Interconnectivity

References [1] C. L. Chaffer, R. A. Weinberg. “A perspective on cancer cell metastasis”, Science , vol. 331, no. 6024, pp. 1559– 1564, 2011. [2] R. C. Rockne et al. , “The 2019 mathematical oncology roadmap”, Phys. Biol. , vol. 16, no. 4, p. 041005, 2019. [3] M. A. Postow et al. , “Immunologic correlates of the abscopal effect in a patient with melanoma”, N. Engl. J. Med. , vol. 366, no. 10, pp. 925–931, 2012. [4] R. H. Mole, “Whole body irradiation—radiobiology or medicine?”, Br. J. Radiol. , vol. 26, no. 305, pp. 234–241, 1953. [5] R. E. Vatner et al. , “Combinations of immunotherapy and radiation in cancer therapy”, Front. Oncol. , vol. 4, p. 325, 2014.

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Digital Poster Simulation of microdosimetry and water radiolysis under ultra-high dose rate with H ⁺ and He² ⁺ beams Daeun Kwon 1 , Alexis Pereda 1 , Giovanna Rosa Fois 1 , Hoang Ngoc Tran 2 , Guillaume Blain 3 , Sophie Chiavassa 4 , Emeline Craff 5 , Sarra Terfas 3 , Manon Evin 3 , Lydia Maigne 1 1 Laboratoire de Physique de Clermont Auvergne, CNRS/IN2P3, Université Clermont Auvergne, Clermont-Ferrand, France. 2 LP2i Bordeaux, UNIVERSITE DE BORDEAUX, Gradignan, France. 3 Laboratoire SUBATECH, CNRS/IN2P3, IMT Atlantique, Université de Nantes, Nantes, France. 4 UNICANCER/ICO, Institut de Cancérologie de l'Ouest, Angers/Nantes, France. 5 R&D, GIP ARRONAX, Nantes, France Purpose/Objective The underlying mechanism of the FLASH effect from physics to biology hasn’t been explained despite studies investigating UHDR (Ultra High Dose Rate) therapy (> 40 Gy/s) and its tissue-sparing effect [1]. The production of Reactive Oxygen Species during water radiolysis stages following radiation exposure is crucial, and Monte Carlo simulations can bring all details of radiolytic species for a long time. To that purpose, we used GATE version 10 as a digital twin of the ARRONAX(Nantes, France) experimental setup with UHDR proton and alpha beamlines, implementing Geant4-DNA chemistry constructors to simulate water radiolysis over time. Material/Methods We used GATE 10 to model proton and alpha beam lines (ARRONAX, IBA Cyclone 70XP). Entrance energy and LET were calculated using a LET actor and a phase space actor, respectively. The experimental setup included protons (68 MeV, range in water: 39 mm), alpha particles (57 MeV, range in water: 3 mm), and dose rates ranging from 40 Gy/s to 350 kGy/s. The Chemistry Actor (including Geant4-DNA constructors) was performed to irradiate an ultra pure water sample (pH=5.5) under different oxygen levels from 0% to 21%. The simulations tracked the evolution of radiolytic yields 1 hour after irradiation, and results were compared to measurements performed in collaboration with the SUBATECH laboratory.