Abstract 17218: Radiation Therapy is not Associated With Incident Atrial Fibrillation in Patients With Thoracic Cancer
Introduction: Radiotherapy for thoracic cancer causes incidental cardiac exposure and increases risk of ischemic heart disease. Less clear is whether radiotherapy similarly increases risk of arrhythmias. Radiotherapy induces cardiac inflammation and fibrosis, which are risk factors for atrial fibrillation (AF).
Hypothesis: In patients with thoracic tumors, radiotherapy is associated with incident AF.
Methods: We conducted a retrospective study of electronic medical records (EMR) of patients who had a primary tumor of the breast, lung, mediastinum, or esophagus diagnosed between 1994 and 2014, did not have AF at time of diagnosis, and did not have previous thoracic radiotherapy. Patients were followed for incident AF until the end of the EMR or death. Incident AF was determined using a validated algorithm with a positive predictive value of 95.6%. After multiple imputation of missing variables, the association between radiotherapy and incident AF was assessed using Cox proportional hazards models.
Results: 4163 patients were included in the analysis. Mean (SD) age was 61.2 (13.3) years and 71% were women; 600 underwent radiotherapy. After a median (25th-75th percentile) 796 (255-2032) days of follow-up, the incidence of AF was 6.8% with and 6.2% without radiotherapy (P=0.538). After adjustment for potential confounders, radiotherapy was not associated with incident AF [hazard ratio (HR): 1.02, 95% confidence interval: 0.72-1.44]. Age [HR (per year): 1.05 (1.04-1.06), P=6.0*10-15], male sex [HR: 2.44 (1.80-3.30), P=9.5*10-9], coronary artery disease [HR: 1.42 (1.06-1.92), P=0.02], hypertension [HR: 6.44 (2.04-20.3), P=0.001], and heart failure [HR: 3.20 (2.31-4.44), P=3.4*10-12] were associated with incident AF. Among 3908 patients with unilateral breast or lung tumors, radiotherapy was not associated with incident AF [HR: 1.23 (0.79-1.92)] and tumor laterality did not modify the effect (P for interaction: 0.201).
Conclusions: In this large retrospective cohort study, radiotherapy for thoracic tumors was not associated with incident AF. Rather, previously described AF risk factors were the most important drivers of AF risk. Larger studies with extended follow-up may further elucidate whether thoracic radiotherapy is a risk factor for AF.
Author Disclosures: R. Lentz: None. B. Chalazan: None. M. Kolek: None. E. Farber-Eger: None. Q. Wells: None. J. Moslehi: None. D. Darbar: None.
- © 2015 by American Heart Association, Inc.