Harvard Women's Health Watch

In the journals: Triple-negative breast cancer rate is triply high in black women

African American women in the United States are less likely to develop breast cancer than white women, but they're more likely to die of the disease, especially at a younger age. Explanations for this disparity include differences in income, education, and access to health care. Researchers have also been investigating biological factors — in particular, an aggressive form of the disease called triple-negative breast cancer, which is more common not only in black women but also in women with BRCA1 mutations and premenopausal women. A study has found that the rate of triple-negative breast cancer is three times higher in African American women than white women. Earlier research indicated that young African American women were especially vulnerable, but this latest research finds that age makes no difference. The results were published in Breast Cancer Research (online, March 25, 2009).

Recognized only in recent years as a distinct subtype, triple-negative breast cancer is so named because it lacks receptors for three substances that fuel most breast cancers: estrogen, progesterone, and human epidermal growth factor 2 (HER2). Some of the best breast cancer therapies — anti-estrogen drugs (tamoxifen and aromatase inhibitors) and the anti-HER2 drug Herceptin — target these receptors and thus are useless in treating triple-negative breast cancer.

The researchers created a database of women treated for invasive breast cancer at Boston University Medical Center. Data included tumor type, grade, stage, and receptor status as well as age, body mass index (BMI), and ethnic group. Among the 415 women in the database, 43% were black; 36%, white; and 10%, Hispanic; the rest were Indian or Middle Eastern. Triple-negative breast cancer was found in 20% of the group as a whole, but black women were disproportionately affected: 30% had triple-negative breast cancer, compared with 11% to 13% in the other groups. Premenopausal and postmenopausal black women were equally affected, and BMI was not a factor. In the group as a whole, the risk of triple-negative breast cancer fell as BMI rose.

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