Breast Cancer Subtypes Based on ER/PR and Her2 Expression: Comparison of Clinicopathologic Features and Survival

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Abstract
To compare the clinicopathologic features and survival in the four breast cancer subtypes defined by immunohistochemistry (IHC) expression of estrogen receptor (ER) or progesterone receptor (PR) and human epidermal growth factor receptor 2 (Her2): ER/PR+, Her2+; ER/PR+, Her2-; ER/PR-, Her2+; and ER/PR-, Her2-. A 7-year retrospective study of 1134 invasive breast cancer subjects. Clinical and pathologic features and survival of the four subtypes were compared. Using ER/PR+ and Her2- as a reference, ER/PR-, Her2- had the worst overall survival (hazard ratio, 1.8; 95% confidence interval [CI], 1.06-3.2) and the worst disease-free survival (hazard ratio, 1.5; 95% CI, 0.8-3.0). In ER/PR+, Her2-, chemotherapy conferred significant overall and disease-free survival advantages. Subtype comparison revealed statistically significant differences in outcomes. The triple negative subtype has the worst overall and disease free survival. Efforts should be directed at standardization of current testing methods and development of more reliable and reproducible testing.