ESTRO 2024 - Abstract Book

S4712

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

ESTR0 2024

the Risks of Breast Cancer Radiotherapy: Evidence From Modern Radiation Doses to the Lungs and Heart and From Previous Randomized Trials. J Clin Oncol. 2017 May 20;35(15):1641-1649.

3. Hooning MJ, Aleman BM, Hauptmann M, Baaijens MH, Klijn JG, Noyon R, Stovall M, van Leeuwen FE. Roles of radiotherapy and chemotherapy in the development of contralateral breast cancer. J Clin Oncol. 2008 Dec 1;26(34):5561-5568. 4. Meijers A, Free J, Wagenaar D, Deffet S, Knopf AC, Langendijk JA, Both S. Validation of the proton range accuracy and optimization of CT calibration curves utilizing range probing. Phys Med Biol. 2020 Feb 4;65(3):03NT02. doi: 10.1088/1361-6560/ab66e1. PMID: 31896099. 5. National Platform for Radiotherapy breast cancer (LPRM), National Platform for Proton Therapy (LPPT), National Platform for Radiation Oncology Hematology (LPRH). National Indication Protocol Proton Therapy Breast cancer. Version 2. 2022 Feb. 6. Wagenaar D, Kierkels RGJ, van der Schaaf A, Meijers A, Scandurra D, Sijtsema NM, Korevaar EW, Steenbakkers RJHM, Knopf AC, Langendijk JA, Both S. Head and neck IMPT probabilistic dose accumulation: Feasibility of a 2 mm setup uncertainty setting. Radiother Oncol. 2021 Jan;154:45-52. doi: 10.1016/j.radonc.2020.09.001. Epub 2020 Sep 6. PMID: 32898561.

2814

Digital Poster

Implications of a target density override in very large moving esophageal tumours treated with IMPT

Sabine Visser, Christina T. Muijs, Margriet Dieters, Petra Klinker, Pietro Pisciotta, Johannes A. Langendijk, Erik W. Korevaar, Stefan Both

University Medical Centre Groningen, Radiation Oncology, Groningen, Netherlands

Purpose/Objective:

Reductions in dose to organs-at-risk (OAR) have been reported using intensity-modulated proton therapy (IMPT) instead of volumetric-modulated arc therapy (VMAT) for esophageal cancer (EC) patients but may be limited due to measures to ensure plan robustness. In our clinic, we apply density overrides to the target volume during plan optimisation, which may increase the proton range, resulting in higher doses to the heart when located at the distal end of the beam, especially for large moving targets. In this study, we evaluate the costs and benefits of applying a target density override in terms of mean heart dose (MHD) and treatment course robustness, respectively, for EC patients with large breathing motion amplitudes.

Material/Methods:

This retrospective study included eight EC patients, who were deemed ineligible for IMPT due to large target motion (18-35 mm) and were treated with VMAT. IMPT plans were generated on the averaged planning 4DCT, either with