ESTRO 2024 - Abstract Book

S4605

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

ESTR0 2024

2 Niemierko A, Schuemann J, Niyazi M, Giantsoudi D, Maquilan G, Shih HA, et al. Brain necrosis in adult patients after proton therapy: is there evidence for dependency on linear energy transfer? Int J Radiat Oncol. 2021;109(1):109–19.

3 Hahn C, Heuchel L, Ödén J, Traneus E, Wulff J, Plaude S, Timmermann B, Bäumer C and Lühr A. Comparing biological effectiveness guided plan optimization strategies for cranial proton therapy: potential and challenges. Radiation Oncology (2022); 17:169

4 McMahon SJ, Paganetti H, Prise KM. LET-weighted doses effectively reduce biological variability in proton radiotherapy planning. Phys Med Biol. (2018); Nov 9;63(22)

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Digital Poster

LETd evaluation of specific organs at risk (OAR) following proton therapy – initial report

Joanna Góra 1 , Mansure Schafasand 1,2 , Ankita Nachankar 1,3 , Marta Mumot 1 , Piero Fossati 1,4 , Markus Stock 1,4 , Carola Lütgendorf-Caucig 1 , Antonio Carlino 1 1 MedAustron Ion therapy Center, Radiation Oncology, Wiener Neustadt, Austria. 2 2) Medical University of Vienna, Radiation Oncology, Vienna, Austria. 3 ACMIT Gmbh, Medical Research and development, Wiener Neustadt, Austria. 4 Karl Landsteiner University of Health Sciences, Radiation Oncology, Krems an der Donau, Austria

Purpose/Objective:

Dose constraints to the various sensitive OARs for patients undergoing proton treatment are quite established already. However, the allowed (safe) dose averaged linear energy transfer (LETd) values are not agreed on yet, especially that there is no consensus on what high or low LETd values for particular dose in proton therapy should be.

421 patients have been treated between 2017-2021 withing REGI-MA0002015 trial, with the median prescribed dose of 58.5 GyRBE (range 40-78 GyRBE) and the median follow up of 24 months.

The purpose of this study was to investigate retrospectively the dose and LETd distributions of selected OARs, e.g. optic system, bulbi, cochleae and brainstem in context of potential toxicities for the patients treated with proton pencil beam scanning at our facility and initiate reporting on those values. Gathered data will hopefully allow correlation between the LETd at specific dose and corresponding side effects.

Material/Methods:

The initial analysis included 25 patients. The RBE-weighted dose in the patients treatment plans was computed with the constant 1.1 RBE, optimized with the single filed or multi field optimization technique (SFO, MFO, respectively), where at least 3-4 beams where applied (spaced>30°). Detailed dose and LETd analysis was performed in the selected OARs and their corresponding dose driven subvolumes. Each of the OARs has been divided into the subvolume that