Menopausal Hormone Therapy and Breast Cancer Findings: Clinical Practice Implications

Purpose of reviewIn a narrative review of randomized clinical trial evidence two major questions regarding menopausal hormone therapy use are addressed. First, do both estrogen-alone and estrogen plus progestin increase breast cancer incidence? Second, in younger postmenopausal women, are there differences in the risk/benefit balance of estrogen-alone versus estrogen plus progestin use which require clinical recognition?Recent FindingsFindings from the two Women's Health Initiative (WHI) randomized, placebo controlled clinical trials evaluating menopausal hormone therapy and breast cancer in postmenopausal women, and from a meta-analysis of other randomized clinical trials evaluating estrogen-alone and breast cancer are summarized and placed in clinical practice context. Relatively short-term, 5.6-year (median) estrogen (as conjugated equine estrogen [CEE]) plus progestin (as medroxy progesterone acetate [MPA]) significantly increases breast cancer incidence through 20-years follow-up. CEE-alone use for 7.2-years (median) significantly decreases breast cancer incidence and significantly decreases breast cancer mortality by 40% through 20-year follow-up. A meta-analysis of 10 randomized trials supports the estrogen-alone effect in reducing breast cancer incidence.SummaryRandomized clinical trial evidence supports a significantly reduced breast cancer incidence and breast cancer mortality with estrogen-alone use. When considered for vasomotor symptom management in younger postmenopausal women, estrogen plus progestin has a less favorable risk/benefit profile than estrogen-alone which warrants clinical recognition.