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 < 0.001), high PLR (HR 1.24; 95%CI 1.06–1.46; p = 0.009), and low LMR (HR 0.67; 95%CI 0.49–0.91; p = 0.01). High NLR and low LMR were also associated with disease-free-survival (HR 1.68; 95%CI 1.35–2.08; p < 0.001 and HR 0.71; 95%CI 0.58–0.87; p < 0.001, respectively). Conclusions: NLR, PLR, and LMR are independent clinical predictors for overall survival in patients with rectal cancer treated with curative surgery. NLR and LMR are also good predictors for disease free survival. These biomarkers, which are readily available, appear optimal prognostic indexes and may help clinicians predict the prognosis of rectal cancer and develop individualized treatment strategies.