Predictors of Atrial Fibrillation After Thoracic Radiotherapy.

in JACC. CardioOncology by Santino Butler, Hyunsoo No, Felicia Guo, Gibran Merchant, Natalie J Park, Scott Jackson, Daniel Eugene Clark, Lucas Vitzthum, Alex Chin, Kathleen Horst, Richard T Hoppe, Billy W Loo, Maximilian Diehn, Michael Sargent Binkley

TLDR

  • The study found that irradiating the pulmonary veins increases the risk of atrial fibrillation in patients undergoing definitive radiotherapy for localized cancers.
  • A dose of 39.7 Gy or greater to the pulmonary veins is associated with a higher risk of atrial fibrillation, regardless of underlying risk factors.

Abstract

Atrial fibrillation (AF) has been associated with thoracic radiotherapy, but the specific risk with irradiating different cardiac substructures remains unknown. This study sought to examine the relationship between irradiation of cardiac substructures and the risk of clinically significant (grade ≥3) AF. We analyzed data from patients who underwent definitive radiotherapy for localized cancers (non-small cell lung, breast, Hodgkin lymphoma, or esophageal) at our institution between 2004 and 2022. The 2-Gy fraction equivalent dose was calculated for cardiac substructures, including the pulmonary veins (PVs), left atrium, sinoatrial node, and left coronary arteries (the left main, left anterior descending, and left circumflex arteries). Competing risk models (subdistribution HRs [sHRs]) for AF incidence were adjusted for the Mayo AF risk score (MAFRS). Among 539 patients, the median follow-up was 58.8 months. The 5-year cumulative incidence of AF was 11.1% for non-small cell lung cancer, 8.3% for esophageal cancer, 1.3% for breast cancer, and 0.8% for Hodgkin lymphoma. Increased AF risk was associated with a higher PV maximum dose (d) (sHR: 1.22;0.001), larger left atrial volume (sHR: 1.01;0.002), greater smoking history in pack-years (sHR: 1.01;0.010), and higher MAFRS (sHR: 1.16;0.001). PV dremained a significant predictor of AF across different MAFRS subgroups (= 0.11), and a PV d>39.7 Gy was linked to a higher AF risk, even when stratified by MAFRS. PV dis a significant predictor of grade ≥3 AF regardless of underlying risk factors. These findings highlight the importance of cardiac substructures in radiation toxicity and suggest that various PV dose metrics should be further validated in clinical settings.

Overview

  • The study aims to investigate the relationship between irradiation of cardiac substructures and the risk of clinically significant atrial fibrillation (AF) in patients undergoing definitive radiotherapy for localized cancers.
  • The study analyzed data from 539 patients who underwent radiotherapy for non-small cell lung, breast, Hodgkin lymphoma, or esophageal cancer between 2004 and 2022.
  • The primary objective is to determine the specific risk of AF associated with irradiating different cardiac substructures and identify predictive factors for AF.

Comparative Analysis & Findings

  • The study found that increased AF risk was associated with a higher maximum dose to the pulmonary veins, larger left atrial volume, greater smoking history, and higher Mayo AF risk score.
  • The pulmonary veins remained a significant predictor of AF across different Mayo AF risk score subgroups, and a dose of 39.7 Gy or greater was linked to a higher AF risk.
  • The study suggests that various pulmonary vein dose metrics should be further validated in clinical settings to inform radiation therapy planning.

Implications and Future Directions

  • These findings highlight the importance of incorporating cardiac substructures in radiation toxicity and suggest that dose metrics should be tailored to specific patient groups.
  • Future studies should investigate the optimal radiation therapy planning strategies for patients with cardiovascular risk factors.
  • The study's results may also contribute to the development of personalized treatment plans for cancer patients with pre-existing cardiac conditions.
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