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

Objective: 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) are ER/PR+,Her2+; ER/PR+,Her2-; ER/PR-,Her2+; and ER/PR-,Her2-. Methods: A 7-year retrospective study of 1134 invasive breast cancer subjects. Clinical and pathologic features and survival of the four subtypes were compared. Results: Using ER/PR+ and Her2- as a reference, ER/PR-,Her2- had worst overall survival (hazard ratio, 1.8; 95 % confidence interval [CI], 1.06-3.2), and 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. Conclusion: Triple negative subtype having worst overall and disease free survival. Efforts should be directed at standardization of current testing methods and development of more reliable and reproducible testing