S1891
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
parameters (Dmean, Dmax, V10–V30) and differentiated DVH for heart substructures, CTV/PTV coverage, and organs-at-risk. Statistical analysis used the Wilcoxon signed-rank test (p < 0.05). Results: Replanning with AHS markedly reduced cardiac doses and across key substructures: mean heart dose decreased from 19.7 Gy to 16.0 Gy ( − 19%), and pericardium Dmean fell by ~9%. Substructure reductions included Dmean AVR 20.2 Gy to 9.7 Gy ( − 52%), SAN 13.8 Gy to 7.2 Gy ( − 45%), right coronary artery (RCA) 15.6 Gy to 10 Gy ( − 38%), left anterior descendent artery (LAD) 13.7 Gy to 8.6 Gy ( − 37%), atrioventricular node (AVN) 28.7 Gy to 18.3 Gy ( − 36%), tricuspid valve (TSV) 21.3 Gy to 14 Gy ( − 35%), right ventricle (RV) 16.6 Gy to 11.5 Gy (-31%), and RA 19.5 Gy to 14.5 Gy ( − 26%), while left atrium and ventricle (LA, LV), and bicuspid valve (BSV) changed minimally. CAA Dmean decreased from 19.5 Gy to 13.8 Gy (-29%) and D1cc from 37.7 Gy to 35.0 Gy ( − 7%). Spatial redistribution of dose effectively reduced high-dose exposure at the heart base. CTV/PTV coverage remained >96%, and lung doses were largely preserved with minor increases in V20 and V30. Conclusion: Heart base–targeted AHS radiotherapy for distal esophageal cancer is feasible and effectively reduces doses to the heart base / CAA, and most cardiac substructures without compromising target coverage, thereby potentially widening the therapeutic window. Modest increases in lung and spinal cord exposure underscore the need to balance cardiac and pulmonary constraints. Prospective studies are warranted to confirm clinical benefits and refine substructure-specific dose guidelines. References: [1] K. Banfill et al., "Brief Report of a New Anatomical Region at Risk in Thoracic Radiotherapy: From Discovery to Implementation," (in eng), JTO Clin Res Rep, vol. 5, no. 12, p. 100742, Dec 2024, doi: 10.1016/j.jtocrr.2024.100742.[2] P. van Hagen et al., "Preoperative chemoradiotherapy for esophageal or junctional cancer," (in eng), N Engl J Med, vol. 366, no. 22, pp. 2074-84, May 31 2012, doi: 10.1056/NEJMoa1112088.[3] A. McWilliam, C. Dootson, L. Graham, K. Banfill, A. Abravan, and M. van Herk, "Dose surface maps of the heart can identify regions associated with worse survival for lung cancer patients treated with radiotherapy," (in eng), Phys Imaging Radiat Oncol, vol. 15, pp. 46-51, Jul 2020, doi: 10.1016/j.phro.2020.07.002. Keywords: esophageal cancer, heart substructures
treatment speed was attributed to the MLC’s larger field shaping capability, reducing the number of required nodes and collimator changes. No statistically significant difference in nCI values was noted between the two planning techniques. Conclusion: The results indicate that the Multileaf Collimator offers clear advantages over the IRIS collimator for CyberKnife SRS of brain AVMs, providing equivalent or superior dosimetric performance while significantly enhancing treatment efficiency. Routine use of MLC collimation may therefore be recommended for AVM radiosurgery to reduce normal brain dose, shorten delivery time, and improve clinical workflow. Future prospective studies with larger cohorts and clinical follow-up are warranted to validate these dosimetric benefits in terms of patient outcomes and toxicity profiles. Keywords: CyberKnife ,MLC,Arteriovenous malformation (AVM) Dosimetric Evaluation of an Active Heart-Sparing Technique Targeting the Heart Base in Esophageal Cancer Radiotherapy Alessandro Clivio 1,2 , Daniel Rudolf Zwahlen 2,1 , Maria Aspradakis 2 , Christoph Oehler 2,1 1 Radiation Oncology, Zentrum für Radiotherapie Rüti Zürich-Ost-Linth, Rüti, Switzerland. 2 Radiation Oncology, Kantonsspital Winterthur, Winterthur, Switzerland Digital Poster 2648 Purpose/Objective: Radiotherapy (RT) is essential in the management of locally advanced esophageal cancer, yet cardiac toxicity remains a major concern, particularly for tumors involving the lower esophagus. Recent studies have identified the heart base—including the right atrium (RA), sinoatrial node (SAN), and aortic valve root (AVR)—as a radiosensitive region associated with increased cardiac morbidity and mortality [1]. Although active heart-sparing (AHS) techniques have demonstrated dosimetric benefits in lung cancer, their feasibility for esophageal tumors adjacent to the heart base has not been explored. This study evaluated AHS RT planning targeting the heart base. Material/Methods: In this single-center retrospective planning study, 20 patients with distal esophageal cancer treated with neoadjuvant chemoradiation (CROSS protocol, 41.4 Gy in 23 fractions) underwent replanning using intensity modulated RT (IMRT) or volumetric modulated arc therapy (VMAT) with lung-derived heart subvolume constraints [1-3]. Original and AHS plans were compared using dose–volume histogram (DVH)
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