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Breast Cancer Health Center

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Hormone Therapy May Skew Mammograms

Abnormal Mammograms Found in Some Women Taking Estrogen and Progestin, Study Shows
WebMD Health News
Reviewed by Louise Chang, MD

Feb. 25, 2008 -- Women who take combined hormone therapy, even for a short time, are at significantly increased risk of having suspicious mammograms and undergoing breast biopsies as a result, new research shows.

New findings from the large, randomized trial that first raised warnings about hormone therapy use and breast cancer suggest that treatment with estrogen and progestin decreases the effectiveness of mammograms and breast biopsies for detecting breast cancer.

In the follow-up of about 8,500 participants in the Women's Health Initiative (WHI) trial, more than one in 10 women who took the hormone combination for five years had suspicious mammograms that they would not have had otherwise, and one in 25 women had avoidable breast biopsies, researchers say.

WHI researcher Rowan T. Chlebowski, MD, PhD, of Harbor-UCLA Medical Center, says women considering combined hormone therapy to treat hot flashes and other symptoms of menopause should definitely be told of the risk.

"The actual increase in (breast cancer) risk associated with taking even combined hormone therapy for this period of time is very small," he tells WebMD. "But a user's risk for having an abnormal mammogram or undergoing a breast biopsy that she may not need is substantial. This is something women considering hormone therapy need to be aware of."

Combined Hormone Therapy Revisited

Chlebowski says the WHI trial offered a unique opportunity to study the impact of hormone therapy on breast cancer screening and detection because all the women who took the combined hormones stopped at the same time, when the study was stopped early because of concerns about heart attack and breast cancer risk.

Millions of other women taking hormones for a host of reasons also stopped taking estrogen plus progestin when the WHI findings were made public.

The therapy is now recommended only for the relief of menopause-related hot flashes and other symptoms, and women are advised to use it in the smallest effective dosage for the shortest possible time.

Of the 16,608 original participants in the trial, 199 women who took the hormones and 150 women who did not take them developed invasive breast cancer over five years.

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