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

Abstract

Purpose

To 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.

Methods

We 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⁻.

Results

Overall, 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.

Conclusion

Disease-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.