Submitted to: International Soy Conference
Publication Type: Abstract Only
Publication Acceptance Date: 8/14/2008
Publication Date: 11/11/2008
Citation: Maskarinec, G., Verheus, M., Cramer, M.A., Lewis, R.D., Murray, M.J., Steinberg, F.M., Young, R.L., Amato, P., Wong, W.W. 2008. Soy isoflavone supplementation and breast density in postmenopausal women [abstract]. The 8th International Symposium on the Role of Soy in Health Promotion & Chronic Disease Prevention, November 9-12, 2008, Tokyo, Japan. Interpretive Summary:
Technical Abstract: Soy isoflavones may protect against breast cancer. Breast density, a marker for breast cancer risk, increases as a result of hormone replacement therapy. We examined the relation between isoflavone supplementation and breast density using the mammograms from 358 women who participated in the multi-site, randomized, double-blind, and placebo-controlled Osteoporosis Prevention Using Soy (OPUS) trial. The postmenopausal women were randomized so that 2/3 of the subjects received 80 or 120 mg/d of isoflavones each and the remaining 1/3 received a placebo for 2 years. After digitizing annual mammograms, percent densities were assessed using a computer-assisted method. The reader was blinded to treatment and timing of mammograms. We applied mixed models to compare breast density by treatment, while considering the repeated measures and adjusting for baseline density and site. At baseline, the groups were similar in age (p = 0.56), body mass index (p = 0.40), and percent mammographic density (p = 0.31), but mean breast density differed by study site (p = 0.02). A model with all mammograms for 358 women did not show a significant treatment effect (p = 0.78). However, time was significant (p <0.001); breast density decreased by 1.6% per year across groups. Based on this 2-year trial, isoflavones do not modify breast density in postmenopausal women.