Prognostic role of platelet-to-lymphocyte ratio, neutrophil-to-lymphocyte, and lymphocyte-to-monocyte ratio in operated rectal cancer patients: systematic review and meta-analysis

Background Inflammation plays an important role in tumor growth. Novel serum blood biomarkers, including neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and lymphocyte-to-monocyte ratio (LMR), have been proposed as useful prognostic indexes in cancer patients. However, their role in rectal cancer is controversial. Methods A comprehensive literature review was conducted including MEDLINE/Pubmed, EMBASE, SCOPUS, and the Cochrane Database of Systematic Reviews through May 2022. The systematic review and meta-analysis were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Quality was appraised with the Methodological Index for Non-Randomized Studies (MINORS) tool. Aim of the study was to summarize available literature on PLR, NLR, and LMR in patients with rectal cancer undergoing resection. Results Forty-seven observational studies (14,205 patients) were included; there were 42 retrospective and 5 prospective cohort studies with an average MINORS score of 14.6 (range: 12–18). Worse overall survival was associated with high NLR (HR 1.81; 95%CI 1.52–2.15; p