Radiation Dose to Cardiac Substructures linked with Different Arrhythmias in Lung Cancer Patients: Study

The study focused on how different doses of radiation to specific heart parts are associated with pathophysiologically distinct classes of arrhythmias.

The researchers identified different arrhythmias linked to radiation doses delivered to specific cardiac substructures. They found that radiation to the pulmonary veins (PVs) was associated with atrial fibrillation (AF) and supraventricular tachyarrhythmia (SVT). In contrast, radiation to the left circumflex coronary artery was connected to atrial flutter. Additionally, radiation targeting the right coronary artery was linked to bradyarrhythmias, and radiation to the left main coronary artery was associated with ventricular tachyarrhythmia (VT) and asystole.

Arrhythmias frequently occur after radiotherapy for non-small cell lung cancer. Katelyn M. Atkins, Department of Cardiology, Cedars-Sinai Medical Center, Los Angeles, California, USA, and colleagues aimed to examine the relationship between different types of arrhythmias and the radiation dose administered to specific cardiac substructures.

For this purpose, the research team performed a retrospective study involving 748 patients with locally advanced non-small cell lung cancer who underwent radiotherapy. The study calculated dose parameters for various cardiac substructures and used receiver-operating characteristic curve analyses to identify predictors for severe atrial fibrillation, atrial flutter, non-AF and non-atrial flutter supraventricular tachyarrhythmia, bradyarrhythmia, and ventricular tachyarrhythmia or asystole. Additionally, Fine-Gray regression models were utilized to account for noncardiac death as a competing risk.

The study led to the following findings:

• Of 748 patients, 17.1% experienced at least 1 grade ≥3 arrhythmia, with a median time to first arrhythmia of 2.0 years.
• The 2-year cumulative incidences of each arrhythmia group were 8.0% for AF, 2.7% for atrial flutter, 1.8% for other SVT, 1.4% for bradyarrhythmia, and 1.1% for VT or asystole.
• Adjusting for baseline cardiovascular risk, pulmonary vein (PV) volume receiving 5 Gy was associated with AF (subdistribution HR [sHR]: 1.04/mL), left circumflex coronary artery volume receiving 35 Gy with atrial flutter (sHR: 1.10/mL), PV volume receiving 55 Gy with SVT (sHR: 1.03 per 1%), right coronary artery volume receiving 25 Gy with bradyarrhythmia (sHR: 1.14/mL), and left main coronary artery volume receiving 5 Gy with VT or asystole (sHR: 2.45/mL).

"These findings emphasize the need for ongoing refinement of cardiac substructure dose limits, taking into account the physiological and pathophysiological mechanisms of cardiac disease," the researchers concluded.

Reference:

Atkins, K. M., Zhang, S. C., Kehayias, C., Guthier, C., He, J., Gasho, J. O., Bakhtiar, M., Silos, K. D., Kozono, D. E., Zei, P. C., Nohria, A., Nikolova, A. P., & Mak, R. H. (2024). Cardiac Substructure Radiation Dose and Associations With Tachyarrhythmia and Bradyarrhythmia After Lung Cancer Radiotherapy. JACC: CardioOncology, 6(4), 544-556. https://doi.org/10.1016/j.jaccao.2024.07.005