The Prognosis of Single Hormone Receptor-Positive Breast Cancer Stratified by HER2 Status

Abstract

Single estrogen receptor (ER)+ and progesterone receptor (PR)+ tumors account for about10% of all breast cancers. However, the prognosis of these single hormone receptor-positive (HR+) tumor remains unclear. We aimed to investigate the characteristics of single HR+ breast tumors according to HER2 status in order to improve the treatment of patients with single HR+. Patients from the SEER program (2010-2016) were divided into ER+PR-, ER-PR+, ER+PR+ and ER-PR- molecular subtypes stratified by HER2 status. Overall survival (OS) and breast cancer-specific survival (BCSS) were compared by Kaplan–Meier curves after propensity score matching (PSM). A total of 203,406 patients were enrolled. Single ER+ and PR+ tumors account for 11.9% of the total population. For HER2- subtype, patients with ER+PR- (n = 16906 pairs) and ER-PR+ (n = 1395 pairs) had worse prognoses than those with ER+PR+ with hazard ratio (HR) and 95% confidence interval (CI) of 1.52 (1.41-1.64) and 2.25 (1.76-2.88) for OS; and 1.94 (1.76-2.14) and 2.57 (1.94-3.40) for BCSS, respectively; ER+PR- showed a better prognosis than ER-PR+ (n = 1394 pairs) and ER-PR- (n = 9626 pairs) with HR (95% CI) of 1.32 (1.06-1.65) and 1.44 (1.33-1.55) for OS, and 1.32 (1.03-1.69) and 1.46 (1.34-1.60) for BCSS, respectively; ER-PR+ had a similar prognosis relative to ER-PR- (n = 1395 pairs) after PSM. For HER2+ subtype, patients with ER-PR+, ER+PR-, and ER-PR- had similar OS and BCSS; ER+PR+ showed a similar prognosis compare with ER-PR+ (n = 535 pairs), but had better OS and BCSS than ER+PR- (n = 5376 pairs) and ER-PR- (n = 8143 pairs) after PSM. In addition, ER+PR+HER2+ showed similar OS and better BCSS compared with ER+PR+HER2- after PSM. In conclusion, single PR+ patients experienced poorer prognoses than single ER+ patients, and may be treated as ER-PR- patients in HER2- subtype. In HER2+ patients, both single ER+ and single PR+ cases showed similar prognoses compared with ER-PR- cases, and may be treated as ER-PR- patients.