Clinical Features and Survival of Single Hormone Receptor–Positive Breast Cancer: A Population-Based Study of 531,605 Patients

Abstract

PurposeTo investigate the prognosis of single hormone receptor–positive (HR+) breast cancer (estrogen receptor [ER] positive and progesterone receptor [PR] negative, and ER−PR+) compared to double HR+ (ER+PR+) and double HR− (ER−PR−) tumors. MethodsWe included 531,605 cases of invasive breast cancer between 1990 and 2012 from the US Surveillance, Epidemiology, and End Results (SEER) database for study and classified cases into 4 phenotypes according to expression of ER and PR: ER+PR+, ER+PR−, ER−PR+, and ER−PR−. ResultsOverall, 66,091 ER+PR− tumors and 9320 ER−PR+ tumors were identified. The clinical characteristics of the ER+PR− group were similar to those of the double HR+ group, while those of the ER−PR+ and double HR− groups were similar. Overall survival of patients with single HR+ tumors was intermediate between that of double HR+ and double HR− tumors. However, we observed no differences in disease-specific survival between ER−PR+ and ER−PR− patients. In multivariate analysis, outcomes were similar. Relative to the double HR+ patient group, risk of death in the ER+PR− group was higher (hazard ratio, 1.422, 95% confidence interval, 1.394-1.452). However, risk of death was comparable between ER−PR+ and ER−PR− patients (hazard ratio, 1.03; 95% confidence interval, 0.98-1.08). Multivariate Cox proportional analysis showed that survival times of patients in the younger age bracket (< 60 years), those positive for human epidermal growth factor receptor 2 (HER2), and patients with tumor stage I-III were longer in the ER−PR+ group. ConclusionDisease-specific survival of single HR+ tumor cases was longer than that of double HR− tumors but poorer than double HR+ tumors. However, differences in disease-specific survival were not significant between the ER−PR+ and ER−PR− groups.