S1742
Physics - Dose prediction/calculation, optimisation and applications for particle therapy planning
ESTRO 2026
Pavia, Pavia, Italy. 5 Dept.of Clinical, surgical, Diagnostic and Pediatric Sciences, University of Pavia, Pavia, Italy
Purpose/Objective: This study aimed to investigate strategies for
optimizing dose-averaged linear energy transfer (LETd) in proton therapy of brain tumors to reduce radiation- induced toxicity in healthy tissues while maintaining target coverage and robustness [1]. The effectiveness of applying LET-based constraints for both fixed and gantry beam geometries was evaluated to develop practical recommendations for safer, more effective planning. Material/Methods: Twenty skull-base tumor patients treated with PT (2018–2025) were included. All received 55.8 GyE in 31
fractions. In total, 136 plans were generated (Figure1): С linical, LETd-optimized plans with
increasing constraints for brain and brainstem (LET 1– 4), and gantry-based plans without (Gantry w/o LET) and with LET optimization (Gantry + LET 1–4). Brain constraints were based on published data: LET 4.6keV/ μ m, dose 43GyE, volume 1cm ³ associated with the risk of necrosis [2] and were made progressively stricter. Reported thresholds for brainstem damage vary considerably and for this study, we used the lowest reported values: LET 2.8 keV/ μ m, dose 50GyE, volume 1 cm ³ and were also made stricter [3]. LETd constraints were applied to auxiliary structures within the brain and brainstem to increase their relative weight during optimization. Plan evaluation included target coverage (D95%), LETd distributions, and robustness against setup/range uncertainties. The clinical relevance of LET reduction in healthy brain tissue was assessed using the NTCP model (normal tissue complication probability).
Conclusion: This work showed that PCCT provides consistent R80 under reduced imaging dose for various phantom sizes and beam orientations, while low dose is inadvisable for large phantoms using DECT. Thus, PCCT could help maintain high treatment accuracy for every patient size and region while reducing CT imaging dose. Keywords: PCCT, Proton range, anthropomorphic phantoms Digital Poster 2815 Clinical implementation of LETd optimization in proton therapy for skull-base tumors Valeriia Tolstoukhova 1,2 , Alessandro Vai 1 , Silvia Molinelli 1 , Sara Lillo 3,4 , Alberto Iannalfi 3 , Alfredo Mirandola 1 , Vittoria Pavanello 1,2 , Alessia Bazani 1 , Stefania Russo 1 , Luca D'ambrosio 3 , Mario Ciocca 1 , Ester Orlandi 5,3 1 Medical Physics, CNAO, Pavia, Italy. 2 IUSS, University of Pavia, Pavia, Italy. 3 Radiation Oncology Unit, Clinical Department,, CNAO, Pavia, Italy. 4 Department of Internal Medicine and Therapeutics, University of
Made with FlippingBook - Share PDF online