Time-trend and recurrence analysis of pancreatic neuroendocrine tumors

This study aimed to evaluate the evolving trends in clinicopathological features of pancreatic neuroendocrine tumors and to analyze the predictors of recurrence after curative resection. Data collected retrospectively from a single center between January 1990 and December 2017 were analyzed. Patients were categorized chronologically into three groups for evolving time-trend analysis. Overall, 542 patients (300 female, 55.4%) underwent surgical resection for pancreatic neuroendocrine tumors, including 435 (80.3%) with non-functional tumors. Time-trend analysis revealed that the surgically resected pancreatic neuroendocrine tumor number increased consistently; however, the incidental non-functional pancreatic neuroendocrine tumor number also increased over time (P < 0.001). The 5- and 10-year disease-free survival rates were 86.4 and 81.3%, respectively. The overall recurrence rate was 13.7%, and the most common site of recurrence was the liver. The median time to recurrence after primary surgery was 19.0 (range 0.8-236.3) months, and the median survival time after recurrence was 22.6 (range 0.4-126.9) months. On multivariate analysis, grade G3 pancreatic neuroendocrine tumors (hazard ratio 4.51; P < 0.001), lymph node metastasis (hazard ratio 2.46; P = 0.009), lymphovascular invasion (hazard ratio 3.62; P= 0.004), perineural invasion (hazard ratio 2.61; P = 0.004) and resection margin (hazard ratio 4.20; P = 0.003) were independent prognostic factors of disease-free survival. The surgically resected pancreatic neuroendocrine tumor number increased over time mainly because of an increase in incidentally discovered non-functional pancreatic neuroendocrine tumors. Grade G3 pancreatic neuroendocrine tumors, lymph node metastasis, lymphovascular invasion, perineural invasion and a positive resection margin were significant predictors of worse disease-free survival in patients with surgically resected pancreatic neuroendocrine tumors.