Patients With Early-Stage Breast Cancer May Have Increased Risk for Atrial Fibrillation

Women with early-stage breast cancer may have a significant (albeit marginal) increased risk for atrial fibrillation (AF) compared with age-matched counterparts without cancer, study findings suggest (JAMA Netw Open. 2019;2[9]:e1911838).


Although several cancer types have been linked to a higher risk for AF, data on early-stage breast cancer (for which cardio-oncology concerns are more pertinent) are limited, explained lead investigator Husam Abdel-Qadir, MD, PhD, Department of Medicine, Women’s College Hospital, Toronto, Ontario, Canada, and colleagues.


Therefore, Dr Abdel-Qadir et al sought to evaluate the relationship between early-stage breast cancer and subsequent chemotherapy with risk for AF by conducting a population-based, retrospective, matched cohort study of 68,113 women with and 204,330 women without the disease (mean age, 60 years).


Patients diagnosed with early-stage breast cancer between April 2007 and December 2016 were matched in a 1:3 ratio to individuals in a cancer-free control group based on birth year and receipt of breast imaging.


AF prevalence before diagnosis of early-stage breast cancer was compared between the cohorts via the McNemar test, and incidence of AF was described using cumulative incidence function curves. Patients were matched with individuals in the control arm before exclusion for prior AF, to assist in the evaluation of preexisting AF.


“For the remaining analyses, we excluded women with prior AF before matching. An analysis was conducted beginning 1 year after the index date (ie, excluding AF diagnoses in year 1), which we stratified by chemotherapy exposure,” Dr Abdel-Qadir and colleagues said.


Hazard ratio (HR) associated with early-stage breast cancer relative to the controls and the link between chemotherapy and AF in patients with the disease were determined via multivariable cause-specific regression.


Among participants with early-stage breast cancer, 44.3%, 38.7%, and 13.4% had stage I, stage II, and stage III disease, respectively; information on cancer stage was missing for 3.6% of the patients.


There were no differences reported in the prevalence of preexisting AF between patients with early-stage breast cancer and controls (5.3% vs 5.2%; P = .21).


At 10 years postdiagnosis, the incidence of AF was 7.4% among patients with early-stage breast cancer (95% CI, 7.1%-7.7%) versus 6.8% among controls (95% CI, 6.7%-7.0%; P <.001). Of note, although the adjusted cause-specific HR was significantly higher at 1 year (HR, 2.16; 95% CI, 1.94-2.41) and after 5 years (HR, 1.20; 95% CI, 1.11-1.30) the same elevation was not seen during years 2 through 5.


Analyses initiated 1-year postdiagnosis demonstrated fewer differences that remained statistically significant—at 9 years’ follow-up, the cumulative incidence of AF was 7.0% for patients with early-stage breast cancer (95% CI, 6.7%-7.3%) and 6.5% (95% CI, 6.3%-6.7%) for cancer-free controls. In addition, although women who received chemotherapy had higher rates of AF (adjusted HR, 1.23; 95% CI, 1.13-1.35) the same was not observed with exposure to anthracyclines or trastuzumab.


“A higher rate of AF was observed in the first year and after 5 years following…diagnosis. The rate of AF was higher in patients who received chemotherapy but appeared to not be associated with specific cardiotoxic agents,” Dr Abdel-Qadir and colleagues concluded.


“These findings suggest that the early and late periods of increased AF risk in EBC [early-stage breast cancer] survivors warrant focused research to better understand the underlying causes and subsequent implications,” they added.—Hina Porcelli

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