Tissue Infiltrating Immune Cells as Prognostic Biomarkers in Endometrial Cancer: A Meta-Analysis

BACKGROUND: The association between tumour-infiltrating immune cells and the prognosis of endometrial cancer (EC) is controversial due to the smaller sample sizes and limited statistical power of the extant studies. We carried out a meta-analysis of the relationship between tumour-infiltrating immune cells and EC survival outcomes. METHODS: A literature search in multiple databases was carried out up to December 2019. Pooled hazard ratio (HRs) and 95% confidence intervals (CIs) were calculated by the Z-test to assess the association between infiltrating immune cells and overall survival (OS), progression-free survival (PFS), relapse-free survival (RFS), disease-specific survival (DSS), and disease-free survival (DFS). A subgroup analysis was performed based on the localisation of immune cells in tumour parenchyma or stroma, immune markers, and the International Federation of Gynecology and Obstetrics stage. Heterogeneity and publication bias between studies were evaluated by Cochran's Q-test and Egger regression test, respectively. RESULTS: Seventeen studies were included in the analysis. The pooled HR of OS, PFS, DSS, and DFS indicated that a high CD8(+) T cell density was associated with a favorable prognosis in EC patients. A significant relationship was found between a high density of CD45RO(+) T cells and a favorable OS in EC patients, but the FoxP3(+) T cell density was not associated with either OS or RFS. A high TAM density was associated with a worse PFS. However, a sensitivity analysis indicated that the findings of PFS and DSS in CD8(+) T cell and PFS in TAM were not robust results. CONCLUSION: This is the first meta-analysis of the relationship between tumour-infiltrating immune cells and the prognosis of EC. High CD8(+) and CD45RO(+) T cell densities in tumours were associated with favorable outcomes in EC patients.