The Prognostic Value of Tumor-Associated Neutrophils in Colorectal Cancer: A Systematic Review and Meta-Analysis

BackgroundTumor-associated neutrophils (TANs) are important components of the colorectal cancer (CRC) microenvironment. However, their role in CRC remains controversial. This study aimed to assess the prognostic value of TANs in patients with CRC. MethodsWe searched the PubMed, EMBASE, and Cochrane Library databases for eligible studies published until January 9, 2023. The pooled hazard ratios (HRs) and odds ratios (ORs) with their 95% confidence intervals (95% CI) were calculated with a random-effects model to assess survival outcomes and clinicopathological features. Subgroup analyses were further conducted to identify potential sources of heterogeneity. Funnel plots and Egger's test were used to measure publication bias. ResultsA total of 19 studies with 7721 patients were included in this meta-analysis. The pooled analysis indicated that high peritumoral TAN infiltration in CRC tissue was significantly associated with favorable cancer-specific survival (HR = 0.57; 95% CI: 0.38-0.86; p = 0.007), but not with overall survival or disease-free survival. No association between high intratumoral or unclear compartment TAN infiltration and CRC prognosis was found. Subgroup analyses showed that the association between TANs and the prognosis of CRC patients differed according to antibody types, tumor stage, quantitative methods, and follow-up time. High intratumoral TAN infiltration was significantly associated with histology type, whereas high TAN infiltration in an unclear compartment was significantly associated with gender, tumor location, and the primary tumor site. ConclusionsHigh TAN infiltration, especially in the peritumoral compartment, could be a potential prognostic marker in CRC. More high-quality studies are required to explore its specific prognostic value in CRC.