The Effects of Bazedoxifene/Conjugated Estrogens on Breast Density in Postmenopausal Women
Dr. Sebastian Mirkin
United States of America
Disclosure : This study was sponsored by Wyeth Research, which was acquired by Pfizer Inc in October 2009.
17 slide(s) – English – 2012-03-28
Objective: To examine the effects of bazedoxifene/conjugated estrogens (BZA/CE) on mammographic breast density.
Design: The Selective estrogens, Menopause, And Response to Therapy (SMART)-5 trial was a 1-year, randomized, double-blind, phase 3 study in non-hysterectomized postmenopausal women. Subjects were randomized to BZA 20 mg/CE 0.45 or 0.625 mg, BZA 20 mg, CE 0.45 mg/ medroxyprogesterone acetate (MPA) 1.5 mg, or placebo. Breast density was assessed in women meeting the inclusion criteria for the breast density substudy via digitized mammograms that were centrally read. Comparisons between active treatment and placebo groups were based on a noninferiority test with a pre-defined margin of 1.5%.
Results: This substudy included 940 participants (mean age ± standard deviation, 54.0 ± 4.0 y): BZA 20 mg/CE 0.45 (n = 231) or 0.625 mg (n = 247), BZA 20 mg (n = 122), CE 0.45 mg/MPA 1.5 mg (n = 100), or placebo (n = 240). At 12 months, BZA 20 mg/CE 0.45 and 0.625 mg showed a decrease in breast density similar to placebo (not statistically different) and demonstrated non-inferiority versus placebo (upper bound of 95% confidence interval [CI], 0.51% and 0.44%, respectively). CE/MPA failed the non-inferiority test and showed a significant increase in breast density versus placebo (P <0.001; 95% CI, 1.1%-2.7%).
Conclusions: BZA/CE did not increase breast density and showed noninferiority versus placebo in contrast to CE/MPA, which increased breast density versus placebo.