Link Found Between Atrial Fibrillation, Chemotherapy Treatment for Early-Stage Breast Cancer

The rate of atrial fibrillation among survivors of early-stage breast cancer treated with chemotherapy was higher than their cancer-free counterparts, according to study results published in JAMA Network Open.¹

However, the results showed a statistical gap: the significantly higher rate among women with early-stage breast cancer, compared with controls, was present in the first year after diagnosis (HR, 2.16; 95% CI, 1.94-2.41) and year 5 after diagnosis (HR, 1.20; 95% CI, 1.11-1.30) – but not during years 2 through 5.

Of note, the rate of atrial fibrillation was higher in women who received chemotherapy (adjusted HR, 1.23; 95% CI, 1.13-1.35); however, this rate was not associated with exposure to anthracyclines or trastuzumab (Herceptin).

Meanwhile, at 10 years, the atrial fibrillation incidence was 7.4% (95% CI, 7.1%-7.7%) for women with early-stage breast cancer and 6.8% (95% CI, 6.7%-7.0%) for the controls (P <.001).

“This translated to approximately one extra case for every 189 women after 10 years,” the researchers wrote.

“This study’s findings suggest that women with early-stage breast cancer may experience a marginal but significant increase in the risk of developing atrial fibrillation compared with age-matched women without cancer,” the researchers wrote.

The population-based, retrospective, matched cohort study included 68,113 women diagnosed with early-stage breast cancer between April 2007 and December 2016. Patients were matched 1:3 with cancer-free controls (n = 204,330) based on birth year and receipt of breast imaging.

Both groups were a mean age of 60 years. Of the women with early-stage breast cancer, 44.3% were diagnosed with stage I disease, 38.7% with stage II, and 13.4% with stage III. Of note, cancer stage information was missing for 3.6% of the patients.

No difference was observed in preexisting AF prevalence (5.3% in the EBC cohort vs 5.2% in controls; P = .21).

The researchers attributed the increased incidence of atrial fibrillation in the first year to temporary factors, including hemodynamic perturbations, fluid shifts, inflammation, or treatment effects other than cardiotoxic agents.

However, they added, the increased prevalence after year 5 could be explained by “a manifestation of survival bias or the worsening cardiometabolic profile and weight gain of (early-stage breast cancer) survivors.”

Limitations included an inability to adjusting for risk factors including obesity and sleep apnea, among other conditions, as determined by the administrative data.

The association of atrial fibrillation and cancer has been addressed in the scientific literature since the mid-20^th century. Three years ago, a trio of Boston University experts wrote in an editorial, published in JAMA Cardiology, that cancer diagnoses after atrial fibrillation was reported in the literature.²

“Clearly many research questions regarding the complex interrelations between (atrial fibrillation) and cancer remain, and with an aging population, represent important areas for future research,” the experts wrote in the editorial. “Further investigation is required to determine whether the presence of (atrial fibrillation) and cancer should modify management strategies given the increased risk of bleeding and thromboembolism observed with both conditions.”

The researchers agreed, concluding that further studies are needed to understand the correlation.

Disclosures:

1. Abdel-Qadir H, Thavendiranathan P, Fung K, et al. Association of Early-Stage Breast Cancer and Subsequent Chemotherapy With Risk of Atrial Fibrillation. JAMA Netw Open. 2019;2(9):e1911838. doi:10.1001/jamanetworkopen.2019.11838.
2. Rahman F, Ko D, Benjamin EJ. Association of Atrial Fibrillation and Cancer. JAMA Cardiol. 2016;1(4):384-386. doi:10.1001/jamacardio.2016.0582.