Bazedoxifene effects on the reproductive tract in postmenopausal women at risk for osteoporosis

The aim of this study was to examine the endometrial, ovarian, and breast safety of bazedoxifene, a novel selective estrogen-receptor modulator, in postmenopausal women at risk for osteoporosis.

Healthy postmenopausal women (N = 1,583; mean age, 57.6 y) with lumbar spine or femoral neck bone mineral density T scores between -1 and -2.5 and/or other clinical risk factors for osteoporosis were enrolled in a 24-month, phase 3, randomized, double-blind, placebo- and active-controlled trial. They received daily treatment with bazedoxifene 10, 20, or 40 mg; placebo; or raloxifene 60 mg. Reproductive safety assessments included periodic transvaginal ultrasound measurements of endometrial thickness, ovarian volume, and presence of ovarian cysts; periodic endometrial biopsies; and adverse event reporting.

Bazedoxifene was not associated with a significant change from baseline in mean endometrial thickness at month 24. The percentage of participants with a change from baseline in endometrial thickness or endometrial thickness greater than 5 mm at month 24 was similar among groups. There was no consensus diagnosis of endometrial hyperplasia or malignancy in the bazedoxifene or raloxifene groups; the rates of other histologic findings, including endometrial polyps, were low (<5%) and similar among groups. No significant between-group differences were found in the change from baseline in ovarian volume, number or size of ovarian cysts, or incidence of ovarian cancer. Reports of breast pain (<4%) and breast cancer (<1%) were low and evenly distributed among groups.

A favorable endometrial, ovarian, and breast safety profile was found after 2 years of treatment with bazedoxifene in healthy, recently postmenopausal women at risk for osteoporosis.