Tamoxifen and mammographic breast densities

The extent of breast tissue density on mammograms Is one of the strongest r isk factors for breast cancer, The aim of this analysis was to evaluate whe ther tamoxifen can affect mammographic breast density. Subjects were partic ipants in the National Surgical Adjuvant Breast Project Breast Cancer Preve ntion Trial (BCPT), recruited and followed at the Breast Center of Saint-Sa crement Hospital in Quebec City, Canada. The Breast Cancer Prevention Trial is a double-blind trial in which women at high risk of breast cancer were randomized to receive either 20 mg tamoxifen per day or placebo. Mammograms were taken before treatment began and yearly thereafter. For the purpose o f this analysis, Wolfe's parenchymal pattern and the percentage of the brea st showing tissue densities were assessed by review of pre- and posttreatme nt mammograms without knowledge of treatment assignment. Among the 69 women included in this analysis, 36 received tamoxifen and 33 received placebo f or an average of 3.3 and 3.5 years, respectively, Among women receiving tam oxifen, 16 of 36 (44.4%) changed to a parenchymal pattern of lower density compared with 5 of 33 (15.2%) women receiving placebo (P = 0.010), Moreover , in the tamoxifen-treated group, the difference in the percentage of the b reast showing tissue densities between the pre- and posttreatment mammogram s reached -9.4% on average compared with a reduction of -3.6% in the placeb o group (P = 0.010), Our data show that tamoxifen can reduce high-risk mamm ographic features. Breast densities should be evaluated as possible early m arkers of the preventive effect of selective estrogen receptor modulators.