ESTRO 2025 - Abstract Book

S3203

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2025

Conclusion: This analysis demonstrates that the interplay effect is negligible for our esophageal and lung cancer patients from dosimetric point of view. Our clinical plans delivered in free breathing are robust against intra-fractional organ motion without volumetric repainting. This robustness is attributed to strict 3D robust optimization and the beam delivery characteristics, such as large spot size, delivery time, and spot sequencing which mitigate the interplay effect. Notably, the overlap between the target and the diaphragm did not show significant interplay enhancement, but it must be evaluated in combination with patient-specific characteristics such as tumor amplitude. References: [1] Vilches-Freixas G, Unipan M, Rinaldi I, Martens J, Roijen E, Almeida IP, Decabooter E, Bosmans G. Beam commissioning of the first compact proton therapy system with spot scanning and dynamic field collimation. Br J Radiol. 2020 Mar;93(1107):20190598. doi: 10.1259/bjr.20190598. Epub 2019 Dec 13. PMID: 31782941; PMCID: PMC7066978. [2] Gajewski, J., Schiavi, A., Krah, N., Rucinski, A., Patera, V., & Rinaldi, I. (2020). Implementation of a Compact Spot Scanning Proton Therapy System in a GPU Monte Carlo Code to Support Clinical Routine. Frontiers in Physics, 8, 578605. https://doi.org/10.3389/fphy.2020.578605 Keywords: Interplay, Proton Therapy, Fractionation