Estrogen Plus Progestin and Breast Cancer Detection by Means of Mammography and Breast Biopsy

Abstract

Menopausal hormone therapy remains in common use by women beginning menopause, with approximately 25 million prescriptions written in a recent year in the United States.¹ For women with a uterus considering combined estrogen plus progestin use, identified breast cancer issues represent a concern. In the Women's Health Initiative (WHI) randomized, placebo-controlled clinical trial, combined conjugated equine estrogen plus medroxyprogesterone acetate use significantly increased the number of mammograms with abnormalities and breast cancers that were larger and diagnosed at more advanced stages.² Despite these results, the effect of combined hormone therapy on breast cancer detection has been unsettled. Although an adverse effect of menopausal hormone therapy on breast cancer detection has been proposed based on observational study findings,^3-5 the results have been mixed.^6,7 In addition, the time course of hormone therapy effects on breast cancer detection has not been described. We therefore examined the effect of combined hormone therapy on breast cancer detection using mammography and breast biopsy throughout the WHI randomized clinical trial comparing combined conjugated equine estrogen plus medroxyprogesterone acetate use with placebo use.