Prognostic significance of CD68+ and CD163+ tumor associated macrophages in head and neck squamous cell carcinoma: A systematic review and meta-analysis

Objective: Tumor associated macrophages (TAMs) are among the most abundant cells of the tumor microenvironment. Several studies have been performed to investigate whether TAM markers, namely CD68 and CD163, could serve as prognostic factors in patients with squamous cell carcinoma of the head and neck (SCCHN). The aim of this systematic review and meta-analysis was to synthetize the available evidence of the literature about the role of CD68+ and CD163+ TAMs as prognostic factors in SCCHN. Materials and methods: This systematic review was performed according to the guidelines reported in the Cochrane Handbook and the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) statement. Meta-analysis of overall survival, disease-free survival and progression-free survival was performed using the inverse of variance test. A random- or a fixed- effect model was used on the basis of the presence of heterogeneity. Risk of bias assessment and subgroup analysis were also performed. Results: High stromal expression of CD163+ TAMs correlated with both poor overall survival (HR, 2.26; 95% CI: [1.47, 3.47]; P < 0.001) and progression-free survival (HR, 2.29; 95% CI: [1.11, 4.71]; P = 0.03). Conversely, abundance of CD68+ TAMs was not associated with overall survival (HR, 1.25; 95% CI: [0.86, 1.80]; P = 0.24) and disease-free survival (HR, 2.06; 95% CI: [0.84, 5.05]; P = 0.11). Conclusions: Findings from this study revealed that whilst IHC analysis of the generic macrophage marker CD68+ has no prognostic utility in patients with SCCHN, the M2-like marker CD163+ predicts poor prognosis. Our data suggest that assessment of CD163+ TAMs in SCCHN has potential for future clinical use. Further well-standardized studies should be performed to confirm these results.