Clinical Characteristics and Outcomes of Single Versus Double Hormone Receptor–Positive Breast Cancer in 2 Large Databases

ABSTRACT Purpose To identify biologic and outcome differences between double-hormone receptor (HR)-positive (dHR+, estrogen receptor (ER)+/progesterone receptor (PgR+)) and single HR-positive (sHR+, either ER+/PgR- or ER-/PgR+) breast cancer and to explore whether the hormone therapy (HT) response in human epidermal growth factor receptor-2 (HER2)-negative breast cancer correlates with the HR status. Methods This retrospective study was conducted with two large breast cancer databases, the Surveillance, Epidemiology, and End Results (SEER) database and the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) clinical dataset. Cox regression analysis was used to estimate overall survival (OS) and breast cancer-specific survival (BCSS) among sHR+ and dHR+ patients. Results In the SEER database, dHR+ patients had significantly longer OS and BCSS than ER+/PgR- patients in a short-term follow-up (OS: hazard ratio=0.620; 95% confidence interval (CI), 0.590-0.652; P Conclusions In HER2-negative breast cancer, sHR+ patients are associated with relatively worse characteristics and worse short-term outcomes than dHR+ patients. Additionally, the outcome of patients receiving HT may differ according to the HR status. However, further studies are needed to confirm these conclusions.