Objective: Breast density is associated with an increased risk of breast cancer. This study assessed changes in mammographic breast density after 24 months of treatment with bazedoxifene (BZA)/conjugated estrogens (CE) in postmenopausal women.
Methods: This was an ancillary study in a subset of nonhysterectomized postmenopausal women enrolled in a randomized, double-blind, placebo-controlled, and active-controlled phase 3 study. Treatments evaluated were BZA 20 mg/CE 0.45 mg, BZA 20 mg/CE 0.625 mg, raloxifene 60 mg, and placebo. Women who were eligible for participation in the ancillary study must have completed 24 months of treatment and have mammograms at baseline and 24 months. The left craniocaudal views from each mammogram pair were digitized and analyzed by a radiologist who was blinded to treatment arm and mammogram date. The percent breast density was determined using validated software.
Results: Mammogram pairs were obtained from 507 evaluable participants (mean age range, 55.2-56.3 y). The mean changes (95% CI) in mammographic breast density from baseline to 24 months were comparable among groups (−0.39% [−0.69 to −0.08], −0.05% [−0.38 to 0.27], −0.23% [−0.54 to 0.08], and −0.42% [−0.72 to −0.11] for BZA 20 mg/CE 0.45 mg, BZA 20 mg/CE 0.625 mg, raloxifene 60 mg, and placebo, respectively). These reductions from baseline were statistically significant for BZA 20 mg/CE 0.45 mg and placebo. The effect of both BZA/CE doses on breast density was generally consistent among subgroups based on age, body mass index, and years since menopause.
Conclusions: Treatment with BZA 20 mg/CE 0.45 mg or BZA 20 mg/CE 0.625 mg for 24 months did not affect mammographic breast density in this population of postmenopausal women.
From the 1Department of Radiology, and 2Division of Midlife Health, Department of Obstetrics and Gynecology, University of Virginia Health System, Charlottesville, VA; 3Department of Obstetrics and Gynecology, Universidade de São Paulo, São Paulo, Brazil; and 4Women’s Health, Pfizer Inc., Collegeville, PA.
Received April 3, 2012; revised and accepted July 3, 2012.
Funding/support: This study was sponsored by Wyeth Research, which was acquired by Pfizer Inc. in October 2009. Medical writing support for this manuscript was funded by Pfizer Inc.
Financial disclosure/conflicts of interest: J.A.H. has received research support from Pfizer Inc. In the past 12 months, J.V.P. has served as consultant (fees to the University of Virginia) to Pfizer Inc., Noven Pharmaceuticals, and Novogyne Pharmaceuticals; received grants/research support (fees to the University of Virginia) from DepoMed, Bionova, and Endoceutics; and received travel funds from Pfizer Inc., Noven Pharmaceuticals, and Novogyne Pharmaceuticals. H.S., S.M., and A.A.C. are employees of Pfizer Inc. E.C.B. has no potential conflicts of interest to disclose.
Data were first presented in poster form at the 93rd Annual Meeting of the Endocrine Society, Boston, MA, June 4 to 7, 2011.
Address correspondence to: Jennifer A. Harvey, MD, Department of Radiology, University of Virginia, PO Box 800170, Charlottesville, VA 22908. E-mail: JAH7W@virginia.edu