The clinical impact of plasma estrogen receptor-1 mutation in patients with metastatic breast cancer: A meta-analysis.

Background: The relevance of the discovered plasma ESR1 mutations in positive metastatic breast cancer (BC) patients who had progressing disease after aromatase inhibitor (AI)-based therapy is still being debated.

Objectives: We conducted this meta-analysis to explore the prognostic and predictive role of plasma ESR1 mutations in patients with progressive BC who have previously received AI therapy.

Material and methods: We searched for relevant studies in the PubMed, Embase and Cochrane Library databases to be included in the meta-analysis. This study was performed to compute combined hazard ratios (HRs) with 95% confidence intervals (95% CIs) for the progression-free survival (PFS) rate and overall survival (OS) rate. Subgroup and sensitivity analyses were also performed. The heterogeneity between studies was evaluated using the I2 statistic.

Results: In this meta-analysis, a total of 1,844 patients with metastatic BC and positive for estrogen receptors (ERs) were enrolled from 8 articles. The analysis revealed that patients with circulating ESR1 mutations had significantly worse PFS (HR: 1.34; 95% CI: 1.17-1.55; p < 0.001) and OS (HR: 1.59; 95% CI: 1.31-1.92; p < 0.001) compared to wild-type ESR1 patients. Subgroup analysis showed that the types of plasma ESR1 mutations were associated with differences in the prognosis of metastatic BC. The D538G mutation showed a statistically significant lower PFS (p = 0.03), while the Y537S mutation was not significantly correlated with PFS (p = 0.354).

Conclusion: According to the findings of this meta-analysis, the assessment for plasma ESR1 mutations may provide prognostic and clinical guidance regarding subsequent endocrine therapy decisions for ER-positive, metastatic BC patients who had received prior therapy with AIs.