Differences in breast cancer rates between racial and ethnic garoups can be largely explained by the distribution of risk factors except in African American women, according to a new study.

Women in ethnic and racial minority groups have lower breast cancer incidence than white women. However, among women with breast cancer, African American women are diagnosed at a more advanced stage, have larger tumors, and are more likely to have estrogen receptor-negative disease than white women. Breast cancer mortality is also higher among African American women than in white women. However, all these differences have remained largely unexplained.

Rowan T. Chlebowski, M.D., Ph.D., of the Los Angeles Biomedical Research Institute in Torrance, Calif., and colleagues examined racial and ethnic differences in breast cancer incidence and outcome in more than 150,000 women participating in the Women's Health Initiative. They found that the lower incidence of breast cancer in Hispanic, Asian/Pacific Islander, and American Indian/Native American women was mostly explained by differences in the distribution of breast cancer risk factors, such as age, family history, reproductive history, education level, and alcohol consumption.

Differences in the distribution of breast cancer risk factors also explained some, but not all, of the difference in breast cancer incidence between African American and white women. Despite the lower incidence of breast cancer in African American women, among those who developed breast cancer, mortality was higher in African American women than in white women. Breast cancers in the African American women were more likely to have the characteristics of poor prognosis tumors than those in other racial and ethnic groups. The authors suggest that the higher rates of obesity and high-grade cancer in African American women could explain som
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Contact: Sarah L. Zielinski
jncimedia@oupjournals.org
301-841-1287
Journal of the National Cancer Institute
15-Mar-2005