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Breast Cancer in Blacks: Less Common, More Deadly

Among Women's Health Initiative participants, black women with breast cancer were more likely than white women to have poor-prognosis tumors.

In this NIH-funded study, investigators assessed racial differences in breast-cancer risk factors, tumor characteristics, and mortality among more than 156,000 postmenopausal women participating in the Women's Health Initiative trials.

During a median follow-up of 6.3 years, 3938 invasive breast cancers were diagnosed. After adjustment for multiple confounders (e.g., age, BMI, parity, hormone therapy use, first- and second-degree relatives with breast cancer, and mammography rate), the risk for breast cancer did not differ between white women and Hispanic, American Indian/Alaskan Native, or Asian/Pacific Islander women. Black women, on the other hand, were at significantly lower risk than white women (hazard ratio, 0.75). Tumor histology, size, and stage did not differ by race/ethnicity. However, a significantly greater proportion of tumors in black women than in white women were both high-grade and estrogen-receptor-negative (32% vs. 10%). In addition, at a median 3.1 years after diagnosis, breast cancer mortality was significantly higher in black women than in white women (8.7% vs. 5.5%).

Comment: Even in the Women's Health Initiative, which provided mammographic screening for the clinical trial participants (42% of the study population), the screening rate was lower in minority women than in white women. However, given that tumor size and stage did not differ between black and white women, less screening does not appear to account for the higher breast cancer mortality in black women. Obesity has previously been associated with high-grade breast tumors, but in the current study, black race was a much more powerful predictor of poor-prognosis tumors than was obesity, suggesting that genetic factors play an important role. Regardless of lower mammography rates and reduced access to healthcare among black women, the higher prevalence of poor-prognosis tumors apparently contributes to higher breast cancer mortality in this population.

— Andrew M. Kaunitz, MD

Published in Journal Watch Women's Health May 3, 2005

Citation(s):

Chlebowski RT et al. Ethnicity and breast cancer: Factors influencing differences in incidence and outcome. J Natl Cancer Inst 2005 Mar 16; 97:439-48.

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