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Hormone replacement may influence mammography accuracy

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SEATTLE, Washington (CNN) -- Women who take hormone replacement therapy may develop denser breast tissue, making it more difficult to detect breast cancer, new research suggests.

The study, published in the Journal of the American Medical Association, found that although the changes in breast density are sustained during hormone use, they are usually reversed when hormones are discontinued.

"The most important message in this study is that the breast changes are not permanent," said Dr. Stephen Taplin, of the Group Health Cooperative of Puget Sound, Seattle, Washington. "Women don't need to worry that their breast tissue will become denser and denser with hormone use and won't change. The study is reassuring."

The American Medical Association has information on many conditions in its Patient Pages:
Breast Cancer Patient Page

Researchers say increased breast density impairs the accuracy of screening mammography and is a strong, if not the strongest, risk factor for missing cancer.

"Although the increase in breast density doesn't happen in all women, we can't predict who's most at risk," said Dr. Mary Laya, one of the study's co-authors. "However, it appears overweight women may be more likely to develop denser breast tissue."

The researchers studied 5,212 postmenopausal women between the ages of 40 and 96. Although a number of studies have looked at what happens to breast tissue when women start using hormone replacement therapy, the impact of continuing and discontinuing hormone use has not been well understood.

"Based on our study, we do not recommend women change their hormone use," said Laya. "We would discourage women from stopping and starting hormone treatment in order to decrease their breast density."

Instead, the study findings should serve as another piece of information women use in deciding whether or not they should use hormones. The study did not find any differences in women taking estrogen and progestin compared to those taking only estrogen.

Researchers say women and prescribing physicians may not be aware of the potential effect of hormones on breast tissue. However, radiologists who do the actual mammography screenings have long known hormone use can change breast tissue.

"We always check a patient's hormone status when reading a mammogram," said Dr. Laurel Lemasters of Atlanta Radiology Consultants. "We also look at other risk factors such as a family history of breast cancer."

A number of studies have shown a link between increased breast density and risk of breast cancer.

"It's more difficult to pick up cancer if breast tissue is dense," said Lemasters, "so a lesion or cancer may be larger in those women when it's detected. That's why it's especially important for women with dense breast tissue to be vigilant about getting mammograms."

Researchers say the decision to use hormone therapy is one a woman should make with her doctor after considering her health history.

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National Cancer Institute: Breast Cancer
American Cancer Society: Breast Cancer Resource Center
National Institute on Aging: Hormone Replacement Therapy
National Cancer Institute: Menopausal Hormone Replacement Therapy
Beth Israel Deaconess Medical Center: Hormone Replacement Therapy

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