Changes in LDL-cholesterol levels following aromatase inhibitor treatment in early postmenopausal breast cancer

There is an unsettled concern that treatment with aromatase inhibitors (AIT) may adversely affect lipid-levels. In light of the improved survival of women with breast cancer and increased risk of atherosclerotic cardiovascular disease in older people, unfavorable effects on lipid-levels may represent a significant health concern for this group of patients. We used linked data from nationwide registries, including a clinical breast cancer database with information about allocated and dispensed AIT. Based on these, we investigated changes in plasma lipid-levels (primary outcome: low-density lipoprotein (LDL)-cholesterol, secondary outcomes: high-density lipoprotein (HDL)-cholesterol, total cholesterol, and triglycerides) following AIT in a nationwide cohort of postmenopausal women with early breast cancer, Denmark, 2009-2020. Included women had at least one LDL-cholesterol measurement before and after breast cancer diagnosis. Exposure was allocated and dispensed AIT as compared with not allocated to and no dispensed AIT. Outcome was the adjusted difference in lipid-level-change (from before to after breast cancer diagnosis) according to AIT. Among 10,461 women, there were 22,693 pre-breast cancer LDL-cholesterol measurements and 42,750 post-breast cancer LDL-cholesterol measurements. Overall, 7919 of the women were exposed to AIT and 2542 women were unexposed. For AIT exposed, the LDL-cholesterol-change was - 0.16 mmol/L (mM), and for unexposed, - 0.15 mM, respectively. The corresponding adjusted difference in LDL-cholesterol change for AIT exposed versus unexposed was - 0.03 mM (95% CI - 0.07 to 0.003). We found similar results in analysis of secondary outcomes. This study does not support the concern that AIT adversely affects lipid-levels.