Advanced stages and poorly differentiated grade are associated with an increased risk of HER2/neu positive breast carcinoma only in White women: findings from a prospective cohort study of African-American and White-American women.

OBJECTIVE: The primary objective of this study was to evaluate the race-specific risk associated with HER2/neu positive breast carcinoma in a prospective cohort design. Our secondary objectives were to assess prevalence of different breast cancer phenotypes between African-American and White women and to determine if race was associated with the risk of basal-like breast carcinoma phenotype in this cohort.

METHODS: Demographic, clinical and pathologic data were collected from existing databases. The status of HER2/neu and hormone receptors was dichotomized as either positive or negative. Immunohistochemistry taxonomy was used to assess prevalence of different breast carcinoma phenotypes. Risk estimates were calculated using the multivariable logistic regression statistics.

CONCLUSIONS: The risk of HER2/neu positive breast carcinoma differs between African-American and White women. For White women only, this risk was statistically significant and increased almost linearly within each TNM stage with grade dedifferentiation. The statistically significantly higher prevalence of "ER(-)/PR(-), HER2(- )" phenotype in African American women potentially is the attributing factor to observed lack of an association between the risk of HER2/neu positive breast carcinoma with advanced stages and poorly differentiated grade. Among women diagnosed with "ER(-)/PR(-), HER2(-)" phenotype the odds ratios of being African-American and pre-menopausal was 1.72 (95% CI 1.17-2.54, P = 0.006) and 1.94 (95% CI 1.27-2.96, P = 0.002), respectively. The histologic features of basal-like and ER(-)/HER2(+ )carcinomas overlaps. Differences in the biology of breast carcinoma between African American and White women are partially attributed to the disparity in more adverse pathologic prognostic indicators at the initial clinical presentation of this disease.