July 30, 2020
Earlier findings published by WHI investigators identified an increased risk of developing breast cancer among clinical trial participants without prior hysterectomy who had received treatment with combination estrogen-plus-progestin hormone replacement therapy over a median of 5.6 years. Conversely, trial participants with prior hysterectomy who underwent estrogen-only therapy for a median of 7.2 years experienced a reduced risk for developing breast cancer. Prior analyses, conducted in 2013 and 2015, noted that these effects endured over a median cumulative follow-up period of 13 years for both therapies.
A recent follow-up analysis, led by WHI investigator Rowan Chlebowski, found that after more than 20 years of median follow-up, the protective effects of estrogen-alone therapy continued to endure, as did the increased risks for developing breast cancer attributed to estrogen-plus-progestin therapy. Despite many years having passed since withdrawal of hormone treatment, the investigators attributed the lasting impacts of each therapy to altered cellular processes in breast tissue affecting cell death (apoptosis). While estrogen-alone therapy is presently not indicated as a prophylaxis for breast cancer due to prior findings suggesting increased risk of stroke and potential influences on hormone-targeted drugs, the authors indicate that other factors may be involved and recommend further work in this arena.
Decisions pertaining to the use and selection of hormone-replacement therapy should be undertaken in partnership with a qualified medical professional and should take into account the numerous personal and health history factors that may influence the benefit/risk calculation of utilizing a particular treatment course.
These findings were published in JAMA in July 2020.
The WHI program is funded by the National Heart, Lung, and Blood Institute, National Institutes of Health, U.S. Department of Health and Human Services.
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