(SLB-023) Cardiovascular Adverse Events of Endocrine Therapies in Women with Breast Cancer: A Disproportionality Analysis Using FAERS

Background: Endocrine therapies (ETs) are widely used in breast cancer treatment; however, emerging evidence suggests potential cardiovascular risks. Understanding these risks is crucial for optimizing treatment decisions and ensuring patient safety.

Objectives: To investigate cardiovascular adverse events associated with oral ETs in women with breast cancer using real-world pharmacovigilance data from the FDA Adverse Event Reporting System (FAERS).

Methods: A retrospective disproportionality analysis was conducted using FAERS reports through December 2023 to evaluate cardiovascular adverse events linked to tamoxifen, letrozole, anastrozole, and exemestane in women with breast cancer. Primary cardiovascular events of interest included myocardial infarction, heart failure, arrhythmia, and stroke. Standardized MedDRA Queries (SMQs) were used to define and classify relevant outcome events. Reporting odds ratios (RORs) and 95% confidence intervals (CIs) were calculated to assess safety signals for each ET regimen compared to all other ETs as the reference group.

Results: A total of 14,327 unique ET-related reports were identified, with anastrozole accounting for the highest proportion (36.2%). Reports from the U.S. were approximately equal to those from all other countries combined. The mean age of patients was the lowest for those receiving tamoxifen (61 years) and was 65, 66 and 67 years for letrozole, anastrozole, and exemestane, respectively. Among all reports, 2,170 cardiovascular events were documented. Heart failure was the most frequently reported event (4.9%), while myocardial infarction was the least (1.2%). Letrozole exhibited the highest reporting rate for adverse cardiovascular events and showed significant safety signals for arrhythmia (ROR = 2.2, 95% CI: 1.8–2.5) and myocardial infarction (ROR = 1.9, 95% CI: 1.4–2.6). Additionally, letrozole use was associated with increased odds of reporting heart failure (ROR = 1.3, 95% CI: 1.1–1.6), while tamoxifen was linked to an increased odds of reporting stroke (ROR = 1.7, 95% CI: 1.5–2.1).

Conclusions: These findings highlight the potential cardiovascular risks of ETs in breast cancer patients. Close monitoring, particularly in high-risk women, is essential to mitigate cardiovascular complications and ensure the safety of long-term treatment. Further research is needed to elucidate the pathways contributing to these adverse events to inform risk stratification and personalized treatment strategies.