PI-29.

Background: Small dense LDL particles are associated with increased atherogenicity. We examined the effect of tamoxifen treatment on LDL subfraction particle size.Methods: 49 breast cancer patients were prospectively followed on adjuvant tamoxifen treatment. LDL peak particle size measurements were performed on plasma using non-denaturing polyacrylamide gradient gel electrophoresis and standardized conditions at baseline and after 4 months of tamoxifen treatment. Genetic variants in the estrogen receptors α[rs#2234693 (PvuII) and rs#9340799 (XbaI)] and β[rs#1256049 (ESR2-01) and rs#4986938 (ESR-02)] were analyzed.Results: The mean LDL particle diameter were 268.09 and 266.82 Å at baseline and after 4 months of tamoxifen treatment respectively (p=0.088). 38 (77%) of the women had LDL Phenotype A at baseline compared to 35 (71%) after 4 months of tamoxifen treatment (P=0.9). The small dense LDL subfraction (phenotype B) was present in 9 (18%) of the women at baseline and 6 (12%) after 4 months of tamoxifen therapy. The baseline LDL major size was not significantly different in pre-and postmenopausal women (270.6 vs. 266.5, P=0.15). The effect of tamoxifen on lipid particle size was similar when analyzed by menopausal status (P=0.24). We found no association between estrogen receptor genotypes and LDL subfractions.Conclusions: Tamoxifen treatment does not alter LDL subfraction particle size in breast cancer patients.Clinical Pharmacology & Therapeutics (2005) 79, P15–P15; doi: 10.1016/j.clpt.2005.12.050 [ABSTRACT FROM AUTHOR]