Hormone Therapy May Skew Mammograms

Abnormal Mammograms Found in Some Women Taking Estrogen and Progestin, Study Shows

Medically Reviewed by Louise Chang, MD on February 25, 2008
From the WebMD Archives

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.

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.

"We have been using lower doses for some time and we've found that in most cases they are just as effective for relieving symptoms," she says.

Jan Shifren, MD, says she believes most women who will accept a slight increase risk in actual breast cancer will not be deterred by the new findings.

Shifren is an associate professor of ob-gyn at Harvard Medical School and Massachusetts General Hospital.

"I don't think this study changes the risk-benefit analysis for menopausal women, and I don't think it will change the minds of many women who have decided they need this treatment," she tells WebMD.

WebMD Health News



Chlebowski, R.T., Archives of Internal Medicine, Feb. 25, 2008; vol 168: pp 370-377.

Rowan T. Chlebowski, MD, PhD, Los Angeles Biomedical Research Institute, Harbor-UCLA Medical Center, Los Angeles.

Robert Smith, PhD, director of screening, American Cancer Society.

Jo Ann Pinkerton, MD, professor of ob-gyn, University of Virginia; president elect, North American Menopause Society.

Jan Shifren, MD, associate professor of ob-gyn, Harvard Medical School and Massachusetts General Hospital, Boston.

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