Prognostic role of lymphocyte to monocyte ratio for patients with cancer: evidence from a systematic review and meta-analysis

Abstract

Inflammation influences cancer development and progression, and a low lymphocyte to monocyte ratio (LMR) has been reported to be a poor prognostic indicator in several malignancies. Here we quantify the prognostic impact of this biomarker and assess its consistency in various cancers. Eligible studies were retrieved from PubMed, Embase and Web of Science databases. Overall survival (OS) was the primary outcome, cancer-specific survival (CSS), disease-free survival (DFS), recurrence-free survival (RFS), and progression-free survival (PFS) were secondary outcomes. Pooled hazard ratios (HRs), odds ratios (ORs), and 95% confidence intervals (CIs) were calculated. Fifty-six studies comprising 20,248 patients were included in the analysis. Overall, decreased LMR was significantly associated with shorter OS in non-hematological malignancy (HR: 0.59, 95% CI: 0.53-0.66; P < 0.001) and hematological malignancy (HR: 0.44, 95% CI: 0.34-0.56; P < 0.001). Similar results were found in CSS, DFS, RFS and PFS. Moreover, low LMR was significantly associated with some clinicopathological characteristics that are indicative of poor prognosis and disease aggressiveness. By these results, we conclude that a decreased LMR implied poor prognosis in patients with cancer and could serve as a readily available and inexpensive biomarker for clinical decision.

Keywords: cancer; inflammation; lymphocyte to monocyte ratio; meta-analysis; prognosis.

Figure 1. Flowchart of selecting studies for inclusion in this meta-analysis

LMR = lymphocyte to monocyte ratio.

Figure 2. The prognostic significance of lymphocyte to monocyte ratio (LMR) in overall survival (OS)

A combined analysis showed that LMR lower than the cutoff was associated with poor OS in non-hematological malignancy (HR: 0.59, 95% CI: 0.53–0.66; P < 0.001) and hematological malignancy (HR: 0.44, 95% CI: 0.34–0.56; P < 0.001) with significant heterogeneity (I² = 53.6% and 77.9%, respectively).

Figure 3. Subgroup analysis of OS by type of cancer and results for the evaluation of publication bias

(A) The lower LMR was significantly associated with poor OS in colorectal carcinoma, lung cancer, nasopharyngeal carcinoma, pancreatic cancer, soft tissue sarcoma, urothelial carcinoma, DLBCL, Hodgkin's lymphoma but not in gastric cancer. (B) The funnel plot for OS of non-hematological malignancy is asymmetric. A publication bias was identified based on Begg's (P = 0.022) and Egger's (P = 0.026) tests. (C) The funnel plot for OS of hematological malignancy is asymmetric. A publication bias was identified based on Begg's (P = 0.208) and Egger's (P < 0.001) tests.

Figure 4. Forest plots for the meta-analysis of the association between LMR and cancer-specific survival (CSS), disease-free survival (DFS) in various cancer types

(A) The lower LMR was significantly associated with poor CSS in colorectal carcinoma, soft tissue sarcoma, Hodgkin's lymphoma and other non-hematological malignancies. (B) The lower LMR was significantly associated with poor DFS in soft tissue sarcoma, DLBCL, other non-hematological malignancies but not in colorectal carcinoma and other hematological malignancies.

Figure 5. Forest plots for the meta-analysis of the association between LMR and recurrence-free survival (RFS), progression-free survival (PFS) in various cancer types

(A) A combined analysis showed that LMR lower than the cutoff was associated with poor RFS in non-hematological malignancy. In addition, a non-significant result for DLBCL was reported. (B) The lower LMR was significantly associated with poor PFS in lung cancer, DLBCL, follicular lymphoma and Hodgkin's lymphoma. In addition, a significant result for Burkitt lymphoma was reported.