Racial disparities in female breast cancer in South Carolina: clinical evidence for a biological basis

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Abstract
Objective. Racial disparities in breast cancer outcomes are well documented: African-American (AA) women have markedly poorer survival than do European-American (EA) women. A growing literature suggests that AA women have, on average, tumors of more aggressive histopathology, even if discovered early. We investigated this in our South Carolina population. Methods. Tumor registry data for 1687 AA and EA women with breast cancers newly diagnosed during 2000–2002 at the two Palmetto Health hospitals in Columbia, SC, were reviewed. Results. Corresponding to our regional population, 31% of cancers were in AA women. In both racial groups, 19% were in situ. Among women with invasive cancers, AA women had significantly earlier age at diagnosis than did EA women. Fewer AA women had lobular carcinoma (p =0.001) or Her-2 over-expressing disease (7 versus 19%, p =0.001). Significantly more AA women had high-grade cancer, larger tumors, axillary metastases and ER negative/PR negative tumors. After controlling for T-stage, AA women were significantly more likely to have high-grade and/or ER negative disease. Detection of invasive cancers by screening mammogram was less frequent in AA women (40 versus 53%, p< 0.000), and in small ER negative cancers. Conclusions. At diagnosis, breast cancers in AA women tend to have the hallmarks of more aggressive and less treatable disease, even in small tumors, a pattern resembling that of breast cancers in younger EA women. Whatever the causes, these observations suggest breast cancer is biologically different in AA women. This may contribute substantially to the poorer outcomes in African-American women.