Comparative effects of anastrozole, tamoxifen alone and in combination on plasma lipids and bone-derived resorption during neoadjuvant therapy in the impact trial

Background: Estrogen has beneficial effects on lipid metabolism and bone preservation. The IMPACT trial evaluated neoadjuvant therapy with anastrozole or tamoxifen alone, or a combination. The comparative effects of these treatments on serum lipids and bone resorption were assessed. Patients and methods: Non-fasting clotted blood samples were taken from 176 postmenopausal patients at baseline, 2 and 12 weeks for assessment of serum levels of estradiol, the bone resorption marker CTx and lipid profiles [total cholesterol (TC), high density lipoprotein cholesterol (HDL-C) and non-HDL cholesterol (N-HDL-C)]. Results: After 12 weeks, tamoxifen was associated with a significant increase in HDL-C (26.5%), and a decrease in TC (6.5%) and N-HDL-C (12.3%). Anastrozole was associated with a significant increase in HDL-C (11.2%), and a non-significant increase in TC (2.9%) and N-HDL-C (3.4%), both of which were significantly different from tamoxifen. The combination was associated with a significant increase in HDL-C (9.4%), and a decrease in TC (10.9%) and N-HDL-C (13.9%). For tamoxifen and the combination, there were non-significant decreases in CTx compared with a significant increase (45.6%) with anastrozole. No correlation between serum estradiol and CTx was seen in any of the treatment groups. Conclusion: Anastrozole did not have a detrimental effect on lipid profiles following 3 months of therapy. There was a significant increase in CTx with anastrozole in contrast to tamoxifen.