Postmenopausal women who take combination estrogen-plus-progestin hormone-replacement therapy (HRT) are significantly more likely to develop dense breast tissue than women who do not take combined HRT, according to a recent study led by Dr. Anne McTiernan, a member of the Public Health Sciences Division at the Hutchinson Center.
This finding is important because increased density of breast tissue reduces the sensitivity of screening mammography.Women with the highest levels of breast density also have a four- to six-times-higher risk of developing breast cancer than women with lower levels of dense breast tissue.
Mammographic density refers to the proportion of cloudy, white areas on a mammogram (connective and epithelial tissues of the breast) and dark-appearing areas (fatty breast tissue).
The findings, published Sept. 21 in the Journal of the National Cancer Institute, were based on data from more than 400 postmenopausal women who participated in an arm of the Women's Health Initiative study designed to assess the risks and benefits of hormone-replacement therapy. Half were randomly assigned to receive daily combined HRT (estrogen plus progestin) and the other half received a dummy pill, or placebo. The study was funded by the National Cancer Institute.
Discuss HRT pros, cons
"For women concerned about their breast-cancer risk, these results may be one more reason to avoid long-term use of HRT," McTiernan said. "Certainly women should discuss the pros and cons of their HRT use with their physicians."
Mean mammographic density among the HRT users increased by 6 percent after the first year of treatment, while breast density decreased by 0.9 percent among those taking the placebo. In addition, the risk of having an abnormal mammogram was nearly four times higher among the HRT users after a year of treatment as compared to the comparison group.
Ask for breast-density report
McTiernan advocates that women become informed about the density of their breast tissue. Radiologists should include a qualitative categorization of breast-tissue density on a woman's mammogram report. "It's not clear how often the woman gets that information," McTiernan said. "Women could ask their physicians to get that information on the report so they can discuss their own situation and what it means for how well their mammograms can be read."
There is no evidence that more frequent mammograms will increase the sensitivity of mammograms in women with dense breast tissue. However, such women may be referred for ultrasound screening or magnetic-resonance imaging in addition to their regular mammograms.
Other co-authors included Center investigators Dr. Ching-Yun Wang and Aaron Aragaki, along with WHI researchers at affiliated clinical centers.
Could taking an aspirin a day reduce mammogram density and thus make it easier for doctors to interpret mammograms? The Hutchinson Center seeks to recruit 144 local women for a study to find out. The primary objective of The Effect of Aspirin on Mammographic Density (TEAM) Study, funded by the Avon Foundation and the National Cancer Institute, is to determine whether a daily dose of regular-strength (325 mg) aspirin decreases mammogram density when taken for six months. Mammogram density appears on a mammogram as a whitish cloudiness, thus making mammograms more difficult to read.
Those eligible are postmenopausal women between 50 and 75 years old with moderate to higher-than-average mammogram density who have not taken hormone-replacement therapy within the past six months.
What participation entails
Participants will be randomized (assigned by chance, like the flip of a coin) to receive either aspirin or an identical-looking placebo capsule for six months. All participants will require two clinic visits; a brief physical exam, including a breast exam; a fasting blood draw and two mammograms. Participants also will be asked to fill out some questionnaires at the beginning and end of the study.
The clinic visits and mammograms will be in the Prevention Center in the Arnold Building. Parking is free.
For more information, call The TEAM Study line at (206) 667-1391 or e-mail firstname.lastname@example.org.