A new publication from the Women’s Health Initiative (WHI) focused on the effects of estrogen and progestin (conjugated equine estrogens 0.625 mg/day and 2.5mg/day medroxyprogesterone acetate = Prempro) on breast cancer incidence mortality after an average follow-up of 11 years, through August 2009. The new information from this now 11 year body of information translates to the primary finding of 1 to 2 extra deaths from breast cancer per 10,000 women per year. These results do not apply to estrogen, as the WHI found no increase in breast cancer risk with estrogen alone among women with a hysterectomy after an average of 7 years on estrogen only.
This increase risk of breast cancer is similar to the increased risk of having menopause 5 years later than other women. These increased risk are considered small although the additional information from this study had also to do with the cancers being more commonly lymph-node positive (81 vs. 43) , as well as more deaths from all causes occurring after a breast cancer diagnosis (51 deaths in the Prempro group vs. 31 deaths in the placebo group. On the other hand, the tumors were similar in histology and grade to breast cancers in the placebo group.
In summary, use of conjugated equine estrogens and progestin increased the risk of breast cancer incidence after 11 years and the cancers were more commonly node-positive with a suggestion of increased mortality.
This research should not be seen as a rationale to refuse any and all menopausal hormone regimes, but rather, using hormone therapy when needed to treat moderate to severe symptoms of menopause, and use the lowest effective dose for the shortest amount of time necessary. Each woman should be evaluated and have a consultation with a menopause expert practitioner to determine her individual needs, priorities and treatment options and then make an informed choice.
Chlebowski R, Anderson G, Gass M, et al. Estrogen plus progestin and breast cancer incidence and mortality in postmenopausal women. JAMA 2010;304(15):1684-1692.