Aromatase Inhibitor Therapy Increases the Risk of New-Onset Atrial Fibrillation in Patients With Breast Cancer

Figure 1. Cohort Selection A total of 10,567 patients with breast cancer treated in Public Hospitals in Hong Kong between January 1, 1999, and December 31, 2020, were selected. 4,625 who received both an aromatase inhibitor and tamoxifen during their disease course were excluded from analysis. 235 cases with history of atrial fibrillation, ventricular tachycardia, or ventricular fibrillation were also excluded from analysis. Among the 5,707 patients analyzed, 4,878 were prescribed an aromatase inhibitor and 829 were treated with tamoxifen. After propensity score matching in a 2:1 ratio, 3,316 patients were included in the final analysis.

Figure 2. Arrhythmia-Free Survival of Patients on Aromatase Inhibitors and Tamoxifen This Kaplan-Meier curve shows that the aromatase inhibitor group had a trend toward higher risk of arrhythmia than the tamoxifen group, with an incidence of 0.625 and 0.306 per 100 patient-years, respectively (crude HR: 2.05; 95% CI: 0.99-4.25; P = 0.053).

Figure 3. New-Onset Atrial Fibrillation-Free Survival of Patients on Aromatase Inhibitors and Tamoxifen This Kaplan-Meier curve shows that the aromatase inhibitor group has a higher incidence of new-onset atrial fibrillation, with an incidence of 0.591 and 0.272 per 100 patient-years, respectively, in the aromatase inhibitor and tamoxifen groups. (crude HR: 2.18, 95% CI: 1.01-4.70; P = 0.046). ∗P < 0.05.

Figure 4. Ventricular Tachycardia or Fibrillation-Free of Patients on Aromatase Inhibitors and Tamoxifen This Kaplan-Meier curve shows that there was no significant difference between the aromatase inhibitor and tamoxifen groups in the incidence of ventricular tachyarrhythmias (P = 0.997).

Figure 5. Ischemic Stroke-Free Survival of Patients on Aromatase Inhibitors and Tamoxifen This Kaplan-Meier curve shows that patients prescribed an aromatase inhibitor had a trend toward higher incidence of ischemic stroke than those prescribed tamoxifen, with an incidence of 0.574 and 0.272 per 100 patient-years, respectively, in the aromatase inhibitor and tamoxifen groups (crude HR: 2.13; 95% CI: 0.984-4.59; P = 0.055).

Figure 6. Myocardial Infarction-Free Survival of Patients on Aromatase Inhibitors and Tamoxifen This Kaplan-Meier curve shows that there was no significant difference between the aromatase inhibitor and tamoxifen groups in the incidence of myocardial infarction (P = 0.326).

Figure 7. Venous Thromboembolism-Free Survival of Patients on Aromatase Inhibitors and Tamoxifen This Kaplan-Meier curve shows that there was no significant difference between the aromatase inhibitor and tamoxifen groups in the incidence of venous thromboembolism (P = 0.575).

Central Illustration. Increased New-Onset Atrial Fibrillation in Patients on Aromatase Inhibitors In our retrospective cohort study utilizing propensity score matching, it was found that the use of aromatase inhibitors (AIs) was associated with an increased risk of new-onset atrial fibrillation (AF) compared with tamoxifen (TMX) in breast cancer patients (crude HR: 2.18; 95% CI: 1.01-4.70; P = 0.04).