A single institution's 21-year experience with surgically resected pancreatic neuroendocrine tumors: an analysis of survival and prognostic factors.

BACKGROUND: Pancreatic neuroendocrine tumors (pNETs) comprise a heterogeneous group of tumors with a varied biological behavior. In the present study, we analyzed the experience of 79 pNETs resected between 1999 and 2014. The pathologic prognostic factors (European Neuroendocrine Tumor Society, ENETS; and AJCC) classification, vascular invasion (VI), proliferation index (ki-67) and the presence of necrosis were retrospectively reviewed. METHODS: The clinical data of 79 patients with pNETs who underwent surgery were retrospectively analyzed. Mortality rates and Kaplan-Meier estimates were used to evaluate survival over time for pathologic stages, tumor functionality, and vascular invasion. Cox proportional hazards models were used to calculate the hazard ratio regarding ENETS, AJCC staging, sex, tumor functionality and vascular invasion. RESULTS: The male:female ratio was 40:39. Twenty-one patients (26%) had functional tumors and 58 (73.4%) had non-functional tumors, of which 35 (44.3%) were diagnosed incidentally. Seventeen Whipple procedures, 46 distal pancreatectomies (including 26 laparoscopic and 20 open procedures), 8 laparoscopic central pancreatectomies, 1 laparoscopic resection of the uncinated process and 7 enucleations (one laparoscopic) were performed. Vascular invasion and necrosis were observed in 29 of 75 cases (38.6%) and in 16 cases (29%), respectively. The comparison between survivor functions of ENETS staging categories showed statistically significant differences (p = 0.042). Mortality rate was higher in patients with non-functioning tumors compared with hormonally functioning tumors (p = 0.052) and in those with vascular invasion (p = 0.186). CONCLUSIONS: In spite of the heterogeneity of pNETs, the ENETS TNM classification efficiently predicts long-term prognosis. The non-functioning tumors and the presence of vascular invasion are associated with poor prognosis.