S791
Clinical - Lung
ESTRO 2026
Randomized evidence for cardiac avoidance of defined substructures in lung radiotherapy is lacking. We emulated a target trial [1] to estimate the causal effect of delivering a lower dose to the Cardiac Avoidance Area (CAA), anewly identified organ-at-risk, on cardiac- related death (CD) in a large cohort of lung cancer patients. Material/Methods: 3,782 patients with non-metastatic lung cancer treated with curative-intent radiotherapy (2010–2016) at two UK centers were analyzed. Pre-existing cardiac disease (PCD) was identified from pre-radiotherapy hospitalizations using ICD-10 codes. The CAA, comprising the right atrium, aortic root, proximal coronary arteries, and superior vena cava, was automatically segmented and doses extracted.The primary outcome was CD from national death certificates, with other causes as competing events. The emulated trial (Table 1) compared two predefined cohorts based on previous findings: Cohort 1: CAA- sparing radiotherapy: maximum CAA EQD2,alpha/beta=3<22.5Gy and Cohort 2: higher-dose radiotherapy: maximum CAA EQD2,alpha/beta=3 ≥ 22.5Gy. The effect of CAA-sparing on CD was evaluated using inverse-probability-of- treatment weighting (IPTW) within marginal structural models. Covariate balance was assessed by standardized mean differences (SMD). Weighted Fine– Gray model estimated the effect of CAA-sparing on CD, adjusting for a priori selected covariates including performance status, age, sex, lung cancer type, tumor volume, nodal involvement, chemotherapy delivery, and PCD. Sensitivity analyses evaluated the association between continuous or restricted cubic splines CAA dose and CD.
Conclusion: Higher SA node radiation dose was associated with increased AF risk. Recognizing the SA and AV nodes as organs at risk may facilitate nodal dose reduction in treatment planning. References: Butler S, No H, Guo F, Merchant G, Park NJ, Jackson S, et al. Predictors of Atrial Fibrillation After Thoracic Radiotherapy. JACC CardioOncology. 2024;6(6):935- 945. doi:10.1016/j.jaccao.2024.08.007.Kim KH, Oh J, Yang G, et al. Association of Sinoatrial Node Radiation Dose With Atrial Fibrillation and Mortality in Patients With Lung Cancer. JAMA Oncology. 2022;8(11):1624- 1634. doi:10.1001/jamaoncol.2022.4202 Loap P, Servois V, Dhonneur G, Kirov K, Fourquet A, Kirova Y. A Radiation Therapy Contouring Atlas for Cardiac Conduction Node Delineation. Pract Radiat Oncol. 2021;11(4):e434-e437. doi:10.1016/j.prro.2021.02.002. Keywords: Arrhythmia, Thoracic Radiotherapy Target Trial Emulation of Dose to a Novel Cardiac Avoidance and Cardiac Related Mortality in Lung Radiotherapy Azadeh Abravan 1,2 , Kathryn Banfill 3 , Alan McWilliam 2 , Thomas Marchant 4 , Bob Wheller 5 , Fei Sun 5 , John Lilley 6 , Kevin Franks 5,6 , Corinne Faivre-Finn 2 , Marcel van Herk 2 1 Institute of genetics and cancer, University of Edinburgh, Edinburgh, United Kingdom. 2 Division of cancer sciences, The University of Manchester, Manchester, United Kingdom. 3 Clinical Oncology, The Christie NHS Foundation Trust, Manchester, United Kingdom. 4 Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, United Kingdom. 5 Oncology, University of Leeds, Leeds, United Kingdom. 6 Oncology, The Leeds teaching hospital NHS, Leeds, United Kingdom Digital Poster Highlight 2500
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