Abstract
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.