Prognostic significance of lymphocyte to monocyte ratio in colorectal cancer: A meta-analysis

Purpose: The lymphocyte to monocyte ratio, an inflammation-based score, has been used to predict the biological behavior of malignant tumors. However, the relationship between the lymphocyte to monocyte ratio and clinical outcomes in patients with colorectal cancer remains controversial. We conducted a meta-analysis to identify the association between the lymphocyte to monocyte ratio and the prognosis of patients with colorectal cancer. Methods: Data were retrieved from PubMed, Embase, and Web of science, the hazard ratio and odds ratios with 95% confidence intervals were used to assess the prognostic value of the lymphocyte to monocyte ratio. Outcomes of interest included prognosis, such as overall survival, disease-free survival, and cancer-specific survival in patients with colorectal cancer. Results: fifteen retrospective, observational, cohort studies involving 11,783 patients were identified. A high lymphocyte to monocyte ratio (LMR) was a significant predictor of better overall survival (hazard ratio = 0.57, 95% confidence interval: 0.52-0.62, P < 0.001), disease-free survival (hazard ratio = 0.77, 95% confidence interval: 0.70-0.84, P < 0.001), and cancer-specific survival (hazard ratio = 0.55, 95% confidence interval: 0.32-0.95, P = 0.031). Increased LMR is also significantly associated with the tumor invasion depth (OR: 0.77, 95% CI: 0.61-0.97) and tumor size (OR: 0.74, 95% CI: 0.61-0.89). Conclusions: Our study indicated that a high lymphocyte to monocyte ratio might be a useful marker for colorectal cancer prognosis. As most of these findings were from retrospective studies, further studies are needed to verify the significance of the lymphocyte to monocyte ratio in clinical practice.