A new study, conducted by Erin Aiello, MPH, and colleagues at Group Health Cooperative's Center for Health Studies, examined the link between HT and breast density among women in a broad range of categories. Her study found:
- Estrogen-only therapy is associated with a small increase in breast density; however, the increase is not as large as the increase in women taking HT with progesterone.
- Longer duration of HT use and older age at first use increase breast density, regardless of the type of HT a woman takes.
- Body Mass Index (BMI), race, age at first menstruation, and family history of breast cancer do not appear to affect the link between breast density and hormone therapy use.
- Use of HT appears to eliminate the known protective effects against breast density that certain characteristics have--namely, older age, having one or more children, and being older at the birth of a first child. This association was strongest among current users of estrogen plus progestin (vs. estrogen only).
"Recent research on hormone therapy has raised lots of questions about how these drugs affect breast density and the sensitivity of mammograms," said Aiello. "Having a better understanding of that link and how it relates to various risk factors may help women and their physicians to better evaluate whether HT is the right choice for them."
Aiello's study is the largest population-based study of its kind, using data from 46,436 women who had received more than 100,000 screening mammograms at Group Health Cooperative between January 1996 and June 2002. At each mammogram, the women completed a questionnaire on breast cancer risk factors, hormone use, health history, and demographics. Aiello and her colleagues analyzed this information along with mammography data and automated pharmacy records that indicated the type of hormone therapy each woman used.
Aiello will present her findings at a meeting of the American Association for Cancer Research in Seattle October 16-19.
The study was funded by a grant from the National Cancer Institute. Other researchers involved in the study were Diana Buist, PhD, of Group Health Cooperative's Center for Health Studies, and Emily White, PhD, of the University of Washington's Department of Epidemiology and the Fred Hutchinson Cancer Research Center.
About Group Health Cooperative and the Center for Health Studies
Group Health Cooperative's Center for Health Studies conducts research related to prevention, diagnosis, and treatment of major health problems. Funded primarily through government and private research grants, the Center is located in Seattle, Washington. Group Health is a consumer-governed, nonprofit health care system that coordinates care and coverage. Based in Seattle, Group Health and Group Health Options, Inc. serve nearly 540,000 members in Washington and Idaho.
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Media Contact: Joan DeClair (GHC) 206-287-2653