Relationship between preoperative inflammatory indexes and prognosis of patients with rectal cancer and establishment of prognostic nomogram prediction model

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Objective: To compare the prognostic evaluation value of preoperative neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), lymphocyte-to-monocyte ratio (LMR), and systemic immune-inflammation index (SII) in rectal cancer patients. Nomogram survival prediction model based on inflammatory markers was constructed. Methods: The clinical and survival data of 585 patients with rectal cancer who underwent radical resection in the First Affiliated Hospital of Xi'an Jiao tong University from January 2013 to December 2016 were retrospectively analyzed. The optimal cut-off values of NLR, PLR, LMR, and SII were determined by the receiver operating characteristic (ROC) curve. The relationship between different NLR, PLR, LMR and SII levels and the clinic pathological characteristics of the rectal cancer patients were compared. Cox proportional risk model was used for univariate and multivariate regression analysis. Nomogram prediction models of overall survival (OS) and disease-free survival (DFS) of patients with rectal cancer were established by the R Language software. The internal validation and accuracy of the nomograms were determined by the calculation of concordance index (C-index). Calibration curve was used to evaluate nomograms' efficiency. Results: The optimal cut-off values of preoperative NLR, PLR, LMR and SII of OS for rectal cancer patients were 2.44, 134.88, 4.70 and 354.18, respectively. There was statistically significant difference in tumor differentiation degree between the low NLR group and the high NLR group (P<0.05), and there were statistically significant differences in T stage, N stage, TNM stage, tumor differentiation degree and preoperative carcinoembryonic antigen (CEA) level between the low PLR group and the high PLR group (P<0.05). There was statistically significant difference in tumor differentiation degree between the low LMR group and the high LMR group (P<0.05), and there were statistically significant differences in T stage, N stage, TNM stage, tumor differentiation degree and preoperative CEA level between the low SII group and the high SII group (P<0.05). The multivariate Cox regression analysis showed that the age (HR=2.221, 95%CI: 1.526-3.231), TNM stage (Ⅲ grade: HR=4.425, 95%CI: 1.848-10.596), grade of differentiation (HR=1.630, 95%CI: 1.074-2.474), SII level (HR=2.949, 95%CI: 1.799-4.835), and postoperative chemoradiotherapy (HR=2.123, 95%CI: 1.506-2.992) were independent risk factors for the OS of patients with rectal cancer. The age (HR=2.107, 95%CI: 1.535-2.893), TNM stage (Ⅲ grade, HR=2.850, 95%CI: 1.430-5.680), grade of differentiation (HR=1.681, 95%CI: 1.150-2.457), SII level (HR=2.309, 95%CI: 1.546-3.447), and postoperative chemoradiotherapy (HR=1.837, 95%CI: 1.369-2.464) were independent risk factors of the DFS of patients with rectal cancer. According to the OS and DFS nomograms predict models of rectal cancer patients established by multivariate COX regression analysis, the C-index were 0.786 and 0.746, respectively. The calibration curve of the nomograms showed high consistence of predict and actual curves. Conclusions: Preoperative NLR, PLR, LMR and SII levels are all correlated with the prognosis of rectal cancer patients, and the SII level is an independent prognostic risk factor for patients with rectal cancer. Preoperative SII level can complement with the age, TNM stage, differentiation degree and postoperative adjuvant chemoradiotherapy to accurately predict the prognosis of rectal cancer patients, which can provide reference and help for clinical decision.