(021) Ischemic Cardiotoxicity of Aromatase Inhibitors in Postmenopausal Women with Early Breast Cancer: an Analysis of Real-World Data

Background: For aromatase inhibitor treatment (AIT) in breast cancer, there is an unsettled concern of cardiotoxicity, particularly ischemic cardiovascular events among women with pre-existing ischemic heart disease (IHD).

Objectives: To investigate the association between AIT and ischemic cardiotoxicity in women with and without previous selected cardiovascular disease (CVD) in a breast cancer cohort that received contemporary treatment.

Methods: In this register-based cohort study, we identified postmenopausal women with early breast cancer from a nationwide clinical breast cancer database, 2009 to 2020. Primary outcome was 2-point major ischemic cardiovascular events (2pMACE) defined as acute myocardial infarction or ischemic stroke and secondary outcome was 5pMACE (acute myocardial infarction, ischemic stroke, unstable angina pectoris, heart failure (HF) or cardiovascular death). We defined selected CVD as IHD, ischemic stroke and HF.

Results: Among 29,118 postmenopausal women with no history of selected CVD, we observed 510 2pMACE among 22,135 women allocated to AIT (incidence rate [IR] 4.3/1000 person-years of follow-up [pyrs]), and 170 2pMACE among 6983 women not allocated to AIT (IR 4.1/1000 pyrs). The risk of 2pMACE was similar in women allocated to AIT vs. no allocation (adjusted HR (adjHR) 0.91, 95% confidence interval [CI] 0.73 - 1.14). Similar was found for 5pMACE (IR 7.0 vs. 5.9/1000 pyrs, adjHR 1.05, 95% CI 0.88 - 1.26) including the individual outcome components except for HF for which adjHR was 1.80 (95% CI 1.16 - 2.79); however, in as-first-treated analysis, we found no association. Results were similar in women with a history of IHD.

Conclusions: This study does not support an ischemic cardiotoxic potential of AIT in female breast cancer patients with or without previous IHD. Further studies are needed to determine the risk of HF.