Abstract PO-077: Use of aromatase inhibitors and risk of cardiovascular disease: A population-based study

Abstract

Abstract Background: Adjuvant endocrine therapy, including aromatase inhibitors (AI) or tamoxifen, is recommended for women diagnosed with estrogen receptor- and/or progesterone receptor-positive breast cancer as it significantly reduces the risk of recurrence and breast cancer-specific mortality. AIs are the preferred treatment for postmenopausal women; however, concerns have been raised with respect to their cardiovascular safety. Some meta-analyses of randomized controlled trials report an increase in cardiovascular disease (CVD) risk with use of AIs compared to tamoxifen; however, “real-world” observational studies have yielded inconsistent findings. Objectives: We aimed to conduct a population-based study in Scotland to investigate whether breast cancer patients treated with AIs are at an increased risk of cardiovascular disease compared to patients treated with tamoxifen. Methods: Women newly diagnosed with breast cancer, from 2009 to 2017, were identified from the Scottish Cancer Registry. AI and tamoxifen use were identified from the nationwide Scottish Prescribing Information System. The primary outcome was CVD, based on incidence or death from CVD obtained from hospital admission and death records, respectively. Cox regression models calculated hazard ratios (HRs) and 95% intervals (CIs) comparing AI use to tamoxifen use and risk of CVD, using an as treated exposure definition. Analyses were adjusted for a range of potential confounders and subgroup analysis investigated risk by CVD subtypes including myocardial infarction, heart failure, ischemic stroke, venous thromboembolism, and angina. Results: The cohort contained 28,712 breast cancer patients, followed for 110,999 person years, during which there were 776 cardiovascular events. Compared to tamoxifen use, AI use was associated with an increased risk of any CVD event (adjusted HR 1.14, 95% CI: 1.02, 1.27), which was particularly marked for ischemic stroke (adjusted HR 1.27, 95% CI: 0.99, 1.63). There were no clear associations for other CVD subtypes. Conclusions: Our preliminary results suggest an increased risk of CVD, and specifically ischemic stroke, in AI users compared to tamoxifen. Additional analyses will be conducted to further investigate these associations, including dose-response. Citation Format: Lauren McVicker, Christopher Cardwell, Úna McMenamin. Use of aromatase inhibitors and risk of cardiovascular disease: A population-based study [abstract]. In: Proceedings of the AACR Virtual Meeting: COVID-19 and Cancer; 2020 Jul 20-22. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(18_Suppl):Abstract nr PO-077.