Triple-negative breast cancers (negative for estrogen receptor [ER], progesterone receptor [PR], and human epidermal growth factor receptor 2 [HER2]), are 3-fold more common in black women than in nonblack women, regardless of age or body mass index (BMI), according to the results of a study reported in the March 25 issue of Breast Cancer Research.

“We investigated clinical and pathologic features of breast cancers (BC) in an unselected series of patients diagnosed in a tertiary care hospital serving a diverse population,” write Lesley A. Stead, from Boston University Medical Center in Massachusetts, and colleagues. “We focused on [Tneg] tumours ([ER], [PR] and HER2 negative), which are associated with poor prognosis.”

Between 1998 and 2006, 415 women were diagnosed with invasive breast cancers and had available data on tumor grade and stage; ER, PR, and HER2 status; and patient age, BMI, and self-identified racial/ethnic group. Using contingency tables and multivariate logistic regression, the investigators evaluated associations between patient and tumor characteristics.

The patient sample had a wide range of racial and ethnic origins, with birthplace representing a total of 44 countries; 36% were white, 43% black, 10% Hispanic, and 11% other. Obesity, defined as BMI higher than 30 kg/m2, was present in 47%. Tumor receptor status was ER+ and/or PR+ in 72%, triple-negative tumors in 20%, and HER2+ in 13%.

Compared with white women, black women had 3-fold higher odds of having a triple-negative tumor (95% confidence interval [CI], 1.6 – 5.5; P = .0001). In black women diagnosed before and after age 50 years, triple-negative tumors were equally prevalent (31% vs 29%; P = not significant). Similarly, prevalence of triple-negative tumors was similar in black women who were obese and nonobese (29% vs 31%; P = not significant). In the overall patient sample, the proportion of triple-negative tumors decreased as BMI increased (P = .08).

Limitations of this study include relatively small sample size and lack of data on clinical outcome or on potential confounders, such as parity.

“Black women of diverse background have 3-fold more Tneg tumours than non-black women, regardless of age and BMI,” the study authors write. “Other factors must determine tumour subtype. The higher prevalence of Tneg tumours in black women in all age and weight categories likely contributes to black women’s unfavorable breast cancer prognosis.”

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