Effect of Letrozole on Plasma Lipids, Triglycerides, and Estradiol in Postmenopausal Women with Metastatic Breast Cancer

Purpose. The aromatase inhibitor letrozole effectively treats breast cancer by decreasing estrogen levels in postmenopausal women. The aim of this prospective study was to evaluate the effect of letrozole on plasma lipids, triglyceride lipase (TGL), and estradiol levels in women with metastatic breast cancer (MBC). Materials and Methods. Fifty-two postmenopausal women with MBC received letrozole, 2.5 mg/day. Blood samples for assessment of plasma levels of total cholesterol (TC), low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol, TGL, and estradiol were taken at baseline and after 3, 6, and 12 months of treatment. Results. A nonsignificant increase was found in TC and HDL cholesterol levels after 3 months, which returned to baseline levels after 6 months (p = .794 and p = .444, respectively). LDL cholesterol increased nonsignificantly after 6 months and returned to baseline thereafter (p = .886). The mean estradiol level was suppressed from 44 pmol/l before treatment to <18 pmol/l after 6 months (p = .014). No difference was found in the estradiol suppression rate whether baseline levels were >40 or <40 pmol/l. Conclusion. Letrozole has a safe effect on the lipid and TGL profiles of postmenopausal women with MBC. Estradiol levels were maximally suppressed within 6 months of treatment. The increased levels of TC during treatment were reversible and returned to normal levels after 3 months. The Oncologist 2010; 15: 1159-1163