Mid- and long-term risk of atrial fibrillation among breast cancer surgery survivors

Background The mid- and long-term risk of incident atrial fibrillation (AF) among breast cancer survivors, especially for younger women, and cancer treatment effects on the association remain unclear. We aimed to investigate the risk of AF among breast cancer survivors and evaluate the association by age group, length of follow-up, and cancer treatment. Methods Using data from the Korean Health Insurance Service database between January 2010 and December 2017, 113,232 women newly diagnosed with breast cancer (aged ≥18 years) without prior AF history who underwent breast cancer surgery were individually matched 1:5 by birth year to a sample female population without cancer (n=566,160). Sub-distribution hazard ratios (sHRs) and 95% confidence intervals (CIs) considering death as a competing risk were estimated, adjusting for sociodemographic factors and cardiovascular/non-cardiovascular comorbidities. Results During follow-up (mean [SD] follow-up, 5.1 [2.1] years), AF developed in 1,166 (1.0%) breast cancer surgery survivors at least 1 year after enrollment. Overall, breast cancer survivors had a slightly increased AF risk compared to their cancer-free counterparts (sHR 1.06; 95% CI 1.00-1.13), but the association disappeared over time. Younger breast cancer survivors (age<40 years) had more than a 2-fold increase in AF risk (sHR 2.79; 95% CI 1.98-3.94), with the association remaining similar over 5 years of follow-up. The increased risk was not observed among older breast cancer survivors, especially those aged>65 years. Breast cancer survivors who received anthracyclines had an increased risk of AF compared to those without the exposure (sHR 1.57; 95% CI 1.28-1.92) over the entire course of follow-up. The association between anthracyclines and AF incidence was also more robust in younger breast cancer survivors (sHR 1.94; 95% CI 1.40-2.69 in those aged ≤50 years). Sensitivity analyses, including further adjustments for obesity and lifestyle factors, supported the results. Conclusions Our findings suggest that younger breast cancer survivors had an elevated risk of incident AF, regardless of the length of follow-up. The use of anthracyclines may increase the mid-to-long-term AF risk among breast cancer surgery survivors.