Abstract PS1-07-08: Association of Prior Thoracic Radiation with Clinical Outcomes in Patients Hospitalized for Atrial Tachyarrhythmias

Abstract Introduction: Thoracic radiation therapy (TRT) is frequently utilized in the management of malignancies such as breast cancer, lymphoma, and lung cancer. While its cardiotoxic effects—particularly coronary artery disease—are well described, less is known about the long-term impact of TRT on arrhythmia-related hospitalizations. This is particularly relevant given the growing population of cancer survivors at risk for cardiovascular disease. Atrial fibrillation and flutter are among the most common sustained arrhythmias in this population, yet outcomes in patients with prior TRT remain poorly characterized. This study examines whether a history of thoracic radiation influences outcomes among patients hospitalized and admitted with atrial fibrillation or flutter. Methods: A retrospective cohort study was conducted using data from the National Inpatient Sample (2016-2022). Atrial tachyarrhythmia hospitalizations were identified using ICD-10 codes for atrial fibrillation and atrial flutter, which likely reflect cases of new-onset arrhythmia or rate-related decompensation. Patients with prior thoracic radiation were identified using corresponding diagnosis codes. Due to coding limitations, atrial tachycardias such as multifocal atrial tachycardia (MAT) and focal atrial tachycardia could not be reliably identified and were therefore excluded—an acknowledged limitation of this study. Multivariable logistic regression was used to calculate adjusted odds ratios (aORs) for binary outcomes, and linear regression was used for continuous outcomes. The primary endpoint was in-hospital mortality; secondary endpoints included total hospitalization charges and length of stay (LOS). Results: Among 3, 198, 304 patients hospitalized primarily for atrial tachyarrhythmias, 8, 570 had a documented history of thoracic radiation. The mean age in the TRT group was 72. 5 ± 6. 21 years, with 52. 9% identifying as male. Prior TRT was associated with a significantly elevated risk of in-hospital mortality (aOR 1. 75; 95% CI: 1. 27-2. 40; p=0. 001). Interestingly, these patients had significantly lower total hospital charges (-9, 356; 95% CI: -11, 893 to -6, 818; p0. 001), while LOS did not differ significantly (+0. 06 days; p=0. 479). Conclusion: A history of thoracic radiation is associated with increased in-hospital mortality among patients admitted for atrial fibrillation or flutter, highlighting the need for vigilant cardiovascular surveillance in this high-risk population. While hospitalization costs were paradoxically lower and LOS was similar, the elevated mortality risk suggests these patients may present with more advanced or treatment-refractory disease. Importantly, our analysis was limited to atrial fibrillation and flutter due to ICD-10 constraints and does not capture other forms of atrial tachycardia such as MAT and focal AT. Future studies with more granular clinical data are needed to fully characterize the spectrum of radiation-associated arrhythmias. Citation Format: A. S. Saini, S. Ghay, R. M. Narasimhan, K. Samimi, R. P. Singh, B. Kaur, P. Ghay, I. B. Dreyfuss, B. Mahal, C. Seldon Taswell. Association of Prior Thoracic Radiation with Clinical Outcomes in Patients Hospitalized for Atrial Tachyarrhythmias abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32 (4 Suppl): Abstract nr PS1-07-08.