Randomized IIB Study of the Effect of Bazedoxifene Plus Conjugated Estrogens on Breast Imaging and Tissue Biomarkers in Peri or Post-Menopausal Women at Increased Risk for Development of Breast Cancer

Phase IIB trial of 6 months of BZA 20 mg +CE 0.45 mg (subsequently designated as BZA+CE) vs a waitlist control. Trial is informed by prior results of a single arm trial that used Duavee® (combination of BZA+CE that is FDA-approved for relief of hot flashes). Since Duavee® is currently not available commercially, the two separate components are used instead. Breast imaging, benign breast tissue by RPFNA, and blood for biomarkers will be obtained at baseline and at 6 months using similar assessment techniques. The primary endpoint is the difference between the BZA+CE and control groups for absolute change from baseline to 6 months in the risk biomarker fibroglandular volume (FGV). Volpara® fully automated assessments overcome the interpretive variance inherent in subjective assessments. Additional endpoints include changes in benign breast epithelial immunolabeling for Ki-67, estrogen receptor alpha (ERα), progesterone receptor (PR), and anterior gradient-2 protein (AGR2); and systemic levels of bioavailable hormones, IGF-1, IGFBP3, and measures of insulin sensitivity. The modifying effects of baseline BMI, visceral adipose, and plasma BZA concentrations on markers will be studied.