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HORMONE THERAPY'S EFFECT ON BREAST DENSITY IS NOT THE SAME FOR ALL WOMEN, GROUP HEALTH STUDY FINDS
Fred Hutchinson Cancer Research Center's Public Health Sciences Division houses the Clinical Coordinating Center for the Women's Health Initiative, or WHI, one of the largest National Institutes of Health-funded studies ever conducted in women. This 15-year, multimillion-dollar study, established in 1991, involves more than 160,000 women nationwide, including some 3,500 in Washington. The WHI Clinical Coordinating Center coordinates the statistical, epidemiologic, nutritional and clinical aspects of the WHI and is responsible for data collection, management and analysis. The Clinical Coordinating Center also plays a key role in clinical, nutritional, laboratory and data quality-assurance activities. Half of the Clinical Coordinating Center resides in the division's Program in Biostatistics, while half resides in the division's Cancer Prevention Program. About Fred Hutchinson Cancer Research Center Fred Hutchinson Cancer Research Center, home of two Nobel laureates, is an independent, nonprofit research institution dedicated to the development and advancement of biomedical technology to eliminate cancer and other potentially fatal diseases. Fred Hutchinson receives more funding from the National Institutes of Health than any other independent U.S. research center. Recognized internationally for its pioneering work in bone-marrow transplantation, the center's four scientific divisions collaborate to form a unique environment for conducting basic and applied science. Fred Hutchinson, in collaboration with its clinical and research partners, UW Medicine and Children's Hospital and Regional Medical Center, is the only National Cancer Institute-designated comprehensive cancer center in the Pacific Northwest and is one of 38 nationwide. In recent years, scientists have discovered that hormone therapy, specifically estrogen plus progesterone therapy, increases breast density, a change that makes it harder to detect breast cancer on mammograms. But it hasn't been clear whether this increase happens for all women, or whether it differs based on various breast-cancer risk factors, the type of HT a woman uses, and the length of time she takes it. 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, 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.
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