Endocrine therapy in early-stage estrogen Receptor-Low breast cancer: a systematic review and Meta-Analysis
A partir d'une revue systématique de la littérature (17 études, 68 894 patientes), cette méta-analyse évalue l'efficacité, du point de vue de la survie sans maladie et de la survie globale, et la toxicité d'un traitement endocrinien chez les patientes atteintes d'un cancer du sein de stade précoce, en fonction du niveau d'expression tumorale du récepteur des estrogènes
Background: Tumors with ≥1% estrogen receptor (ER) expression by immunohistochemistry (IHC) are classified as hormone receptor-positive. While this definition includes ER-low tumors (ER 1-9%), the clinical benefit of endocrine therapy (ET) in ER-low early-stage breast cancer (BC) remains uncertain.
Methods: This is a systematic review and meta-analysis of studies in early-stage ER-positive, HER2-negative BC reporting (i) ET efficacy within ER-low tumors and/or (ii) outcomes comparing ER-low versus ER-rich disease. Ovid MEDLINE, Embase, and conference abstracts were searched through January 2025. Endpoints were disease-free survival (DFS) and overall survival (OS). Random-effects meta-analyses were performed to derive pooled hazard ratios (HRs) with 95% confidence intervals (95% CI). Heterogeneity was assessed with the I² statistic.
Results: Of 8,982 records screened, 17 studies were included, comprising 10,232 patients with ER-low tumors and 58,662 with ER-rich disease. Among the ER-low group, receipt of ET was associated with a reduction of 33% in the risk of relapse or death (HR 0.67, 95% CI 0.54-0.85, I²=0%) and of 22% in the risk of death (HR 0.78, 95% CI 0.68-0.90; I²=19.2%). Compared with ER-rich disease, ER-low tumors had inferior outcomes for both DFS (HR 2.18, 95% CI 1.58-3.00; I²=78%) and OS (HR 2.08, 95% CI 1.30-3.31; I²=95.8%).
Conclusions: In patients with ER-low tumors, ET use was associated with improved outcomes. These findings support consideration of ET in early-stage ER-low disease and the inclusion of these patients in trials evaluating novel ET-based therapies, alongside therapeutic approaches appropriate to their higher baseline risk of relapse.
Journal of the National Cancer Institute , résumé, 2026