Neutrophil-to-lymphocyte ratio predicts metachronous liver metastasis of pancreatic neuroendocrine tumors

Background Pancreatic neuroendocrine tumors (PNETs) are clinically malignant, having metastatic potential. Histological tumor grade is an accepted indicator of malignant potential, but noninvasive prognostic markers have not yet been identified. This study assessed whether the preoperative neutrophil-to-lymphocyte ratio (NLR) could predict clinical outcomes of PNET patients. Methods Fifty-eight patients who underwent curative resection for PNETs between 2001 and 2015 were retrospectively evaluated. The correlations between the preoperative NLR and clinicopathological parameters, including patient baseline clinical characteristics, tumor progression, and postoperative oncological outcome were evaluated. Results A high preoperative NLR was significantly associated with large tumor size (P = 0.0015) and high tumor grade (P < 0.0001). Overall survival and relapse-free survival of patients with a high NLR (>= 2.4) were significantly shorter than those of patients with a low NLR (< 2.4, P = 0.0481 and P < 0.0001, respectively). Multivariate analysis revealed that NLR >= 2.4 and tumor size >= 2 cm were independent predictors of postoperative recurrence (hazard ratio 6.012, P = 0.0035 and 6.760, P = 0.0049, respectively). Interestingly, a high NLR independently predicted postoperative liver, but not lymph node, metastasis. Conclusions In this patient series, a high NLR (>= 2.4) was a noninvasive marker that independently predicted postoperative liver metastasis in patients with PNETs, and thereby could be clinically useful.