A randomised study comparing the effects of anastrozole and letrozole on lipid metabolism.
Authors: FM McCaig, L Renshaw, L Williams, O Young, J Murray, EJ Macaskill, M McHugh, R Riermersma, JM Dixon
Journal: Cancer Research (2009)

Abstract Abstract #1152 Background:&amp;#x2028; Aromatase inhibitors (AIs) reduce circulating oestrogen which may have a detrimental effect on lipid metabolism. Letrozole (L) decreases circulating oestrogen levels to a greater degree than anastrozole (A). This study compares the effects of adjuvant anastrozole and letrozole on lipid metabolism.&amp;#x2028; Patients and Methods:&amp;#x2028; This was an open, randomised pharmacodynamic study. Plasma lipids were measured in a subset of 57 out of 182 postmenopausal women with invasive ER positive breast cancer. As part of their adjuvant hormone therapy, patients were randomized to receive either&amp;#x2028; · 12 weeks of L followed by 12 weeks of A (L→A) or&amp;#x2028; · 12 weeks of A followed by 12 weeks of L (A→L).&amp;#x2028; Fasting blood and urine samples were collected at the same time of day and the same day at entry and after 12 weeks of each drug.&amp;#x2028; · 29 had no prior tamoxifen and&amp;#x2028; · 27 had received tamoxifen.&amp;#x2028; The following lipoproteins were measured:&amp;#x2028; - Triglyceride - HDL&amp;#x2028; - Cholesterol - ApoA1&amp;#x2028; - ApoB&amp;#x2028; - Cholesterol&amp;#x2028; - cLDL&amp;#x2028; HDL and ApoA1 are cardioprotective whereas ↑ levels of the others are associated with an ↑ risk of coronary artery disease.&amp;#x2028; Results:&amp;#x2028; (Expressed as absolute changes +/- 95% CI)&amp;#x2028; Patients who stopped tamoxifen &amp;gt;12 weeks prior to trial entry were considered tamoxifen free. Patients who had stopped tamoxifen &amp;lt;12 weeks prior to trial entry were considered to have tamoxifen in their system at trial entry.&amp;#x2028; A vs L: &amp;#x2028; There were no significant differences detected between A and L.&amp;#x2028; A vs L in tamoxifen vs no tamoxifen groups:&amp;#x2028; Triglycerides. Both A and L resulted in a significant decrease in triglycerides in patients who had tamoxifen in their systems, A = -0.02 (-0.24, 0.20) and L = 0.08 (-0.13, 0.29) vs those with no prior tamoxifen A = 0.51 (0.35, 0.68) and L = 0.56 (0.39, 0.72). A p = 0.0003 and L p = 0.001 respectively.&amp;#x2028; ApoB. Both A and L resulted in a significant decrease in ApoB in patients who had tamoxifen in their systems, A = 0.78 (0.64, 0.91) and L = 0.84 (0.71, 0.97) vs those with no prior tamoxifen A = 0.92 (0.82, 1.02) and L = 0.91 (0.80, 1.01). p = 0.03 for both drugs.&amp;#x2028; HDL. A resulted in a significant increase in HDL in patients who had tamoxifen in their systems 1.68 (1.49, 1.86) vs those with no prior tamoxifen 1.38 (1.24, 1.53) p = 0.02.&amp;#x2028; There were no significant changes for any other variables measured.&amp;#x2028; Conclusions:&amp;#x2028; There were no significant differences between letrozole and anastrozole in their effects on lipids.&amp;#x2028; Patients who had recently completed tamoxifen and commenced anastrozole or letrozole showed beneficial changes in their lipid profile compared to patients with no tamoxifen in their systems. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1152.