Clinical value of circulating <em>ESR1</em> mutations for patients with metastatic breast cancer: a meta-analysis.

Background: The clinical implication of plasma ESR1 mutations in the estrogen receptor (ER)-positive metastatic breast cancer (MBC) patients who had progressed after prior aromatase inhibitor (AI)-based therapy remains controversial. We conducted the first meta-analysis to investigate the prognostic significance and predictive role of plasma ESR1 mutations in MBC patients with prior exposure to AI therapy. Materials and methods: We searched PubMed, Embase, and Cochrane Library databases for eligible studies. Meta-analysis was conducted to calculate combined hazard ratios (HRs) with 95% CIs for progression-free survival (PFS) and overall survival (OS). Subgroup and sensitivity analyses were also performed. Results: This study enrolled a total of 1,530 patients with ER-positive MBC cases from six articles, including 429 ESR1 mutation carriers (28.04%). Meta-analysis demonstrated that plasma ESR1 mutation carriers had significantly worse PFS (HR: 1.40, 95%&#160;CI: 1.17–1.66; P [ABSTRACT FROM AUTHOR]