Gynecologic Safety of Conjugated Estrogens Plus Bazedoxifene: Pooled Analysis of Five Phase 3 Trials

OBJECTIVE: To evaluate gynecologic safety of conjugated estrogens/bazedoxifene treatment for menopausal symptoms and osteoporosis prevention in nonhysterectomized women. MATERIALS AND METHODS: We pooled data from five randomized, placebo-controlled trials of conjugated estrogens 0.625 mg/bazedoxifene 20 mg (n = 1583), conjugated estrogens 0.45 mg/bazedoxifene 20 mg (n = 1585), and placebo (n = 1241). Gynecologic safety was evaluated by pelvic examination, Papanicolaou smear, endometrial biopsy, transvaginal ultrasound, mammogram, adverse events, and diary records of vaginal bleeding and breast pain/tenderness. Incidence rates and relative risks (RR) versus placebo were calculated with inverse variance weighting. Data for conjugated estrogens 0.45 mg/medroxyprogesterone acetate 1.5 mg, an active comparator in two trials (n = 399), are included for comparison. RESULTS: Endometrial hyperplasia occurred in <1% (n = 4 0.3%, 2 0.2%, 1 0.5%, and 2 0.2% for conjugated estrogens 0.625 mg/bazedoxifene 20 mg, conjugated estrogens 0.45 mg/bazedoxifene 20 mg, conjugated estrogens/medroxyprogesterone acetate, and placebo). There was one endometrial cancer, which occurred with conjugated estrogens 0.45 mg/bazedoxifene 20 mg (0.44/1000 woman-years 95% confidence interval (CI), 0.00-2.37; RR versus placebo 0.91 95% CI, 0.17-4.82). There were seven cases of breast cancer: four with conjugated estrogens 0.45 mg/bazedoxifene 20 mg (1.00/1000 woman-years 95% CI, 0.00-3.21 RR 1.11 95% CI, 0.33-3.78), two with placebo, and one with conjugated estrogens/medroxyprogesterone acetate. Unlike conjugated estrogens/medroxyprogesterone acetate, conjugated estrogens/bazedoxifene did not increase breast density, breast pain/tenderness, or vaginal bleeding versus placebo. No active treatment increased ovarian cysts. CONCLUSION: Conjugated estrogens/bazedoxifene provides endometrial protection without increasing breast pain/density, vaginal bleeding, or ovarian cysts in nonhysterectomized postmenopausal women studied up to 2 years.