Association between estrogen receptor gene polymorphisms and breast density in postmenopausal women

Objectives The aim of this study was to evaluate the association between clinical characteristics and polymorphisms HaeIII, MspI and XbaI of the estrogen receptor gene alpha with postmenopausal mammographic density. Methods A prospective study was performed with 120 women who were not users of hormones and had no identified breast lesions. All of them underwent bilateral mammography; the radiological density was determined by three independent observers, with two subjective evaluations based on the ACR-BIRADS(R) classification of mammographic patterns, 2003, and one computerized evaluation using the gray-scale histogram tool of the Adobe Photoshop(R) 7.0 software. Peripheral blood samples were obtained for DNA extraction, performed according to the GFX(R) Kit protocol (Amersham-Pharmacia). Polymerase chain reaction restriction fragment length polymorphism was carried out for an analysis of the polymorphisms present in intron 1 (HaeIII and XbaI) and in exon 1 (MspI) of the estrogen receptor gene. Results There was a high degree of concordance among the observers in the determination of mammary density (Kappa, Pearson and Spearman, p < 0.001). The associations of clinical characteristics with mammary density were: age (p = 0.04), body mass index (p < 0.0001) and age at menarche (p = 0.02). The relationship between the allele distribution of the polymorphisms and density was: XbaI (p = 0.02), HaeIII (p = 0.65) and MspI (p = 0.65). Conclusions Our data suggested that the polymorphism XbaI may be strongly related to mammographic density.