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Breast Cancer Health Center

Hormone Therapy May Skew Mammograms

Abnormal Mammograms Found in Some Women Taking Estrogen and Progestin, Study Shows
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Combined Hormone Therapy Revisited continued...

Compared with women who did not take the hormones, women taking them had a 4% greater risk of having an abnormal mammogram after one year of hormone use and an 11% greater risk after five years of use.

To put it another way, roughly one in three women who took the hormones (35%) had abnormal mammograms, compared with slightly less than one in four (23%) placebo-treated women.

Breast biopsies were also more common in women taking hormones, with 10% having biopsies compared with 6% of women in the placebo arm of the study.

Biopsies led to a diagnosis of breast cancer in 15% of women taking estrogen and progestin and just under 20% of women who did not take hormones.

The updated WHI findings appear in the Feb. 25 issue of the Archives of Internal Medicine.

"This shouldn't scare anybody away from taking combined hormone therapy if they need it," Chlebowski says. "But women on the fence may decide that the extra risk of having a mammogram that needs follow-up isn't worth it."

The Experts Weigh In

Hormone therapy can make the breasts denser, and denser breasts are harder to image.

But earlier findings by Chlebowski and colleagues suggest that changes in breast density alone do not fully explain the increase in abnormal mammograms seen in women taking combined hormone therapy.

He says that his previous research has not shown an increase in mammograms that require biopsies in women taking estrogen alone.

American Cancer Society Director of Screening Robert Smith, PhD, says the findings add to the evidence that the risks of combined hormone therapy outweigh the benefits for many menopausal women.

"Unless a woman's quality of life is completely compromised (by menopause symptoms), on balance she would be better off avoiding hormones," he tells WebMD.

But North American Menopause Society incoming President Jo Ann Pinkerton, MD, tells WebMD that the breast cancer risk associated with short-term use of combined hormones is quite small for menopausal women.

Clinicians now routinely prescribe lower doses of hormones than were given to the women in the WHI trial in an effort to further reduce the risk.

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