Effect of postmenopausal hormonal replacement therapy on mammographic density and parenchymal pattern.

Abstract

To measure changes and predictors of change in mammograms obtained in postmenopausal women undergoing continuous combined hormonal replacement therapy (HRT). Mammograms of 41 postmenopausal women obtained before and 1 year after the initiation of HRT were evaluated blindly according to the quantitative density percentage method and the Wolfe classification system. Mammographic densities increased compared with baseline values in 73% of subjects (mean increase, 6.7%; 95% confidence interval, 2.5%, 11.0%; P = .003). A shift in Wolfe classification from lower to greater parenchymal density was noted in 24% of subjects (P = .016). Multivariate analysis results indicated that the lower the tissue density percentage before treatment, the greater the increase in density percentage after treatment. An increase in mammographic density was demonstrated in most subjects undergoing continuous combined HRT and was most pronounced in subjects with a lower baseline density percentage.