ESTRO 2025 - Abstract Book

S2935

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2025

Material/Methods: Participants with lung cancer treated with curative-intent radiotherapy underwent longitudinal assessments including cardiac biomarkers, ECG, echocardiogram and cardiac CT, as part of the ACcoLade trial. Treatment planning was performed with IMRT or VMAT on 4DCT with intravenous contrast. Cardiac chambers were auto segmented on the average image projection using Limbus version v1.8B3, and manually reviewed and edited by a clinical oncologist, following the Milo atlas. Myocardial wall structures were created through isotropic contraction of the exterior chamber structures using in-house software. This process was informed by margins derived from a subset of patients who underwent cardiac CT (n=10) and the cardiac radiology literature. No planning organ volume at risk margins were applied. Absolute dose-volume histogram summary statistics (mean, V5, V20, V50) and structure volumes were extracted for whole chambers and myocardial walls and compared with R 2 coefficients. Results: The average myocardial wall thicknesses were 6mm for the left ventricle and 2mm for other chambers. Treatment plans for 94 patients were analysed; 69% conventional or mild hypofractionation and 31% stereotactic treatment. Intravenous contrast was used in 93% patients. The mean heart doses were 12.8Gy and 2.4Gy respectively. Dosimetric comparison of the cardiac chambers and myocardial walls revealed a very high degree of correlation across all four cardiac chambers for all dose metrics (R 2 ≥0.96) ( Table 1 ). Structure volumes were also highly correlated (R 2 0.89–0.99) ( Table 1 ).

Conclusion: Dose metrics for the cardiac chambers and myocardial walls are highly correlated in patients with lung cancer treated with standard-of care radiotherapy, supporting the continued use of whole chamber contours in future cardiotoxicity research. The increasing availability of high-quality cardiac substructure auto-segmentation tools should be leveraged in studies investigating novel biomarkers of radiotherapy-related cardiac toxicity, ideally in large, real-world databases that account for baseline cardiac health.

Keywords: Cardiac substructures, radiation dose, lung cancer

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Digital Poster Impact of mixed technique on breast radiotherapy treatment: a preliminary study Nicola Padula 1 , Anna Sardo 1 , Luca Frassinelli 2 , Simone Baroni 2 , Claudio Scaffidi 2 , Rachele Petrucci 2 , Giorgio Bosticardo 1 , Gianni Intermite 1 , Alessia Reali 2 , Francesco Lucio 1 1 ASL CN2, Medical Physics, Verduno, Italy. 2 ASL CN2, Radiotherapy, Verduno, Italy Purpose/Objective: Breast cancer treatment planning can be performed using different techniques such as conformational radiotherapy, IMRT, or VMAT.