Despite an overall decline in invasive breast cancer in the United States in recent years, African-American women, particularly younger ones, have not seen a significant decline in their rates, according to researchers at the University of Pittsburgh. These findings, which are being presented at the American Public Health Association (AHPA) Annual Meeting in Boston, Nov. 4 ? 8, strongly suggest the need for additional research to understand why these differences persist and to determine whether avoidable or preventable factors account for these puzzling patterns, according to the investigators.
Excluding cancers of the skin, breast cancer is the most common cancer among women. According to the American Cancer Society, in 2006, breast cancer will account for nearly one out of every three cancer diagnoses in women in the United States, with an estimated 212,920 women developing the disease. About 40,000 U.S. women die of the disease each year. Although white women have the highest overall breast cancer incidence rates, African-American women under age 40 have a significantly higher incidence of breast cancer as well as a higher rate of death from breast cancer than do white women. Furthermore, African-Americans with breast cancer die at a younger age than women in other groups.
To further investigate racial disparities in breast cancer incidence, researchers from the University of Pittsburgh Cancer Institute?s (UPCI) Center for Environmental Oncology, collaborating with researchers from Pitt?s Graduate School of Public Health (GSPH), analyzed breast cancer incidence among African-American and white women in the United States from 1975 to 2002. This study found that the chances of getting breast cancer in newer generations are about 21 percent higher in whites and 41 percent higher in African-Americans than in previous generations of women.
The researchers attributed much of the increased incidence among white women to better detection, due to the widespread availability of mammographic screening beginning in 1994, and to the use of hormone replacement therapy. However, because mammographic screening is not typically recommended for younger African-American women, increased detection or changes in medical practice cannot explain the patterns of breast cancer seen in this ethnic group.
According to lead investigator Devra L. Davis, Ph.D., M.P.H., director of the UPCI Center for Environmental Oncology and professor of epidemiology, GSPH, these findings suggest that significant resources and research need to be directed toward understanding why younger African-American women are at significantly higher risk of developing breast cancer.
?The good news is that rates of invasive breast cancer are on the decline overall. However, African-American women, particularly younger women, have not shared in this trend. We need to find out very quickly why this is and take immediate steps to rectify the problem,? she emphasized.
Although there are many potential factors that could contribute to the difference in breast cancer incidence among African-American women and white women, environmental factors are strong candidates, according to Dr. Davis. In particular, certain hormone-mimicking compounds, such as bisphenol A, a widely used plasticizer, and preservatives, called parabens, that are frequently used in personal care products, including deodorants, antiperspirants and many cosmetic, food and pharmaceutical products, have been shown to accelerate breast cancer cell growth in cell cultures.
In an upcoming paper in the journal Medical Hypotheses, Dr. Davis, along with Maryann Donovan, Ph.D., M.P.H., scientific director, UPCI Center for Environmental Oncology, and their colleagues suggest that the use of estrogen and other hormone-containing personal care products by younger African-American women may account, in part, for their increased risk of breast cancer prior to menopause when developing breasts are subjected to elevated estrogen exposure during critical windows of vulnerability. These exposures also may explain why relatively more African-American women die of breast cancer than do their white counterparts. The paper calls for public disclosure by manufacturers of personal care products of proprietary hormonally active ingredients in their products so that research can move forward.
In addition to Dr. Davis, others involved in this study include Ji Young Song, UPCI Center for Environmental Oncology, and Yueh Ying Han and Joel L. Wessfield, M.D., GSPH.