Impact of diabetes mellitus on the prognostic value of the neutrophil-lymphocyte ratio in renal cell carcinoma

The aim of the present study was to evaluate the effect of diabetes mellitus (DM) on the neutrophil-lymphocyte ratio (NLR)-based prediction of the prognosis of patients with renal cell carcinoma (RCC). The data of 662 patients who had undergone nephrectomy for RCC between January 2004 and July 2014 were retrospectively reviewed. X-tile analysis was used to determine the optimal cutoff value for the NLR. Kaplan-Meier curves were drawn and the log-rank test was applied to determine the impact of the NLR (high vs. low) on the overall survival (OS) and metastasis-free survival (MFS). Univariate and multivariate Cox regression analyses were used to identify prognostic factors for OS and MFS. The median follow-up period after surgery was 50.35 months (range, 30.30–85.08 months). The optimal cutoff value of the NLR was determined to be 3.2 using X-tile software. In the analysis of total subjects, patients with a high NLR (≥3.2) had significantly worse OS and MFS rates than those with a low NLR (<3.2) (21.60% vs. 78.40%, P=0.001 for OS and 21.60% vs. 78.40%, P<0.0001 for MFS). In the non-DM subgroup, the OS and MFS rates of patients with a high NLR were significantly worse compared with those of patients with a low NLR (21.69% vs. 78.31%, P=0.003 for OS and 21.69% vs. 78.31%, P<0.001 for MFS). In the DM subgroup, although a high NLR was still associated with the MFS (NLR≥3.2, 21.43% vs. NLR<3.2, 78.57%; P=0.015), it was no longer associated with the OS (NLR≥3.2, 21.43% vs. NLR<3.2, 78.57%; P=0.192). Furthermore, multivariate analysis identified the NLR as a risk factor for OS and MFS in all patients [hazard ratio (HR)=1.77, 95% confidence interval (CI): 1.04–3.01, P=0.037; and HR=2.31, 95% CI: 1.45–3.70, P<0.001, respectively) and in the non-DM subgroup (HR=2.03, 95% CI: 1.05–3.93, P=0.036; and HR=2.57, 95% CI: 1.47–4.49, P=0.001, respectively), but not in the DM subgroup (P>0.05). In conclusion, DM is a factor that impairs the evaluation of the prognosis of RCC using NLR.