Prognostic value of lymphocyte-to-monocyte ratio in patients with solid tumors: A systematic review and meta-analysis

Background: The immune system plays an important role in cancer pathogenesis. A low lymphocyte-tomonocyte ratio (LMR), as a simple biomarker of host immune system, has been suggested to be related to poor prognosis in various cancers. We performed a systematic review and meta-analysis to quantify the prognostic value of LMR on clinical outcomes in non-hematologic solid tumors. Patients and methods: We searched PubMed and the ASCO online database of meeting abstracts up to July 2015 for relevant studies. We included studies assessing the prognostic impact of pre-treatment LMR on clinical outcomes in patients with non-hematologic solid tumors. The primary outcome was overall survival (OS) and the secondary outcomes were cancer-specific survival (CSS) and disease-free survival (DFS). The summary hazard ratio (HR) and 95% confidence interval (CI) were calculated. Results: A total of 11,197 patients from 29 studies were included. LMR lower than the cut-off was associated with poor OS (HR, 1.73; 95% CI, 1.55-1.93; P < 0.001), CCS (HR, 1.56; 95% CI, 1.27-1.91; P < 0.001) and DFS (HR, 1.56; 95% CI, 1.31-1.86; P < 0.001). The effect of LMR on OS was observed in among various tumor types and across disease stages. The median cut-off value for LMR was 3.0 (range = 2.0-5.3). Subgroup analysis according to cut-off value (<3.0, 3.0 to <4.0, 4.0 to <5.0, and ≥5.0) showed a significant prognostic value of LMR on OS in all subgroups. Conclusions: A low pre-treatment LMR seems to represent an unfavorable and robust prognostic factor for clinical outcomes in patients with non-hematologic malignancies. Funding: None.