Survival Benefit of Adjuvant Endocrine Therapy for Hormone Receptor Low-Positive Breast Cancer: A Propensity Score-Weighted Analysis

Abstract

Abstract Purpose: To investigate the survival benefit of adjuvant endocrine therapy in women with hormone receptor low-positive breast cancer.Methods: A retrospective search of the prospectively maintained database of our academic medical center identified women with unilateral hormone receptor low-positive (1–10%) primary invasive breast cancer who underwent surgery between January 2003 and December 2015. Disease-free survival (DFS) and overall survival (OS) were compared between women who received and did not receive adjuvant endocrine therapy using propensity score-weighted analysis of clinical, imaging, and pathologic factors.Results: Of 448 women (median age, 51 years), 84 (19%) had recurrence (20 locoregional, 10 contralateral, and 54 distant metastases) and 51 (11%) died during a median follow-up of 7.9 years. The DFS and OS for women who received (n = 320) and did not receive (n = 128) adjuvant endocrine therapy were not different in the propensity score-weighted log-rank test (P = 0.43 for DFS; P = 0.48 for OS) and Cox proportional regression analysis (hazard ratio [HR] for DFS, 0.8; P = 0.42; and HR for OS, 1.3; P = 0.48). The survival benefit of adjuvant endocrine therapy was observed in the subgroup of women who did not receive adjuvant radiation therapy (HR, 0.5; P = 0.04 for DFS and HR, 0.4; P = 0.046 for OS) (P for interaction < 0.05).Conclusion: No survival benefit was observed with adjuvant endocrine therapy in women with hormone receptor low-positive breast cancer. Strategies are needed to optimize adjuvant endocrine therapy effectiveness in this population.