Predicting Aggressive Behavior in Nonfunctional Pancreatic Neuroendocrine Tumors With Emphasis on Tumor Size Significance and Survival Trends: A Population-Based Analysis of 1787 Patients

Background: Nonfunctional pancreatic neuroendocrine tumors (NF-PNETs) are rare tumors with continued controversies in management. This study aims to identify demographic and clinicopathologic characteristics associated with aggressive behavior and survival. Methods: The Surveillance, Epidemiology, and End Results database was used to identify patients with NF-PNETs from 1988 to 2012. Multivariate regression analysis and Cox proportional hazards modeling were used to assess the impact of patient, tumor, and treatment characteristics on tumor behavior and overall survival. Results: In 1787 patients identified, size was a major determinant of aggressive behavior. The probability of aggressiveness increased 100% for tumor size >= 2 cm. For tumors >= 2 cm, every I -cm increase in size was associated with an increase in probability of aggressive behavior by 11.3%. Patient age, tumor grade, and surgical resection were independent predictors of survival. Surgical resection was associated with improved survival but not grade I or II tumors with size <2 cm. Discussion: Patient age, tumor size, and grade should be in the decision-making process around the surgical management of NF-PNETs. For tumors <= 2 cm with histologic grades of I or II, the probability of aggressive behavior is low, and surgical resection does not appear to afford survival benefit. Therefore, close observation could be justified.