Elevated Peripheral Absolute Monocyte Count Related to Clinicopathological Features and Poor Prognosis in Solid Tumors: Systematic Review, Meta-analysis, and Meta-regression

Background: Absolute monocyte count (AMC) is often used to be assessed in cancer follow-up, which has regained interest as a potential prognostic indicator in many solid tumors, though not consistently or comprehensively. In the present study, we set out to perform a comprehensive meta-analysis of all available data regarding the prognostic significance of AMC in solid tumors. We also evaluated the association between AMC and clinical features in solid tumors.

Methods: A hazard ratio (HR) and corresponding 95% confidence interval (CI) or a p value (p) from eligible studies were extracted and subsequently pooled analyzed. Subgroup analyses and meta-regression analyses were conducted according to the confounders of included studies. In addition, the relationships between AMC and clinical characteristics were also explored in the meta-analysis.

Results: Overall, ninety-three articles comprising 104 studies with 32229 patients were finally included. The results showed that elevated AMC was associated with worse overall survival (OS) (HR = 1.615; 95% CI: 1.475-1.768; p < 0.001), disease-free survival (DFS) (HR:1.488; 95% CI: 1.357-1.633; p < 0.001), progressive-free survival (PFS) (HR: 1.533; 95% CI: 1.342-1.751; p < 0.001) and cancer-specific survival (CSS) (HR: 1.585; 95% CI: 1.253-2.006; p < 0.001) in non-hematological tumors. Subgroup analyses according to each confounder further proved the consistent prognostic value of AMC in solid tumor outcomes. Moreover, elevated AMC was more likely to be observed in male group and patients with smoking history, and associated with longer tumor length and advanced T stage.

Conclusion: In short, the meta-analysis found that elevated AMC might indicate poor long-term outcomes in non-hematologic cancers, thus AMC may be a valuable marker in the prognosis for patients with solid tumors.