Comparison of changes in the lipid profile of postmenopausal women with early stage breast cancer treated with exemestane or letrozole

Effects of aromatase inhibitor (AI) therapy on the plasma lipid profile are not clear. Here the authors describe changes in fasting lipids (total cholesterol, high-density lipoprotein [HDL], low-density lipoprotein [LDL], and triglycerides) before and after 3 months of exemestane or letrozole treatment. HDL was reduced in the entire cohort (P <.001) and in the exemestane group (P <.001) but unchanged in the letrozole group (P =.169). LDL was increased in the entire cohort (P =.005) and in the letrozole group (P =.002) but unchanged in the exemestane group (P =.361). This effect was at least partially attributable to washout of tamoxifen as only patients with prior use of tamoxifen experienced a significant increase in LDL. Baseline HDL was an independent predictor of the change in HDL (r2 = -0.128, P <.001), and prior tamoxifen use was associated with greater increases in LDL (r2 = 0.057, P <.001). Use of lipid-altering medications did not protect against the exemestane-induced drop in HDL or the increase in LDL observed in women with prior use of tamoxifen taking letrozole. In conclusion, AI treatment and/or washout of tamoxifen induced detrimental changes in the lipid profile of postmenopausal women with breast cancer.