Background: Nonfunctional pancreatic neuroendocrine tumors (PNETs) ≤2 cm have uncertain malignant potential, and optimal treatment remains unclear. Objectives of this study were to better understand their malignant potential, determine whether extent of surgery or lymph node dissection is associated with overall survival (OS), and identify other factors associated with OS.
Methods: Patients with nonfunctional PNETs ≤2 cm were identified from the National Cancer Data Base (1998 to 2011). Descriptive statistics were used for patient characteristics and surgical resection patterns. Five-year OS was estimated using Kaplan-Meier analyses across extent of surgery and compared using the log-rank test. Cox proportional regression modeling was used to test the association between survival and extent of surgery.
Results: A total of 1854 patients with nonfunctional PNETs ≤2 cm were included. From 1998 to 2011, these tumors increased three-fold as a proportion of all PNETs. Among tumors ≤0.5 cm, 33 % presented with regional lymph node metastases and 11 % with distant metastases. Five-year OS for patients not undergoing surgery was 27.6 % vs. 83.0 % for partial pancreatectomy, 72.3 % for pancreaticoduodenectomy, and 86.0 % for total pancreatectomy (p < 0.01). Multivariate analysis demonstrated no difference in OS based on type of surgery or the addition of regional lymphadenectomy (p = 0.16). Younger age and later year of diagnosis were independently associated with improved survival.
Conclusions: Small nonfunctional PNETs represent an increasing proportion of all PNETs and have a significant risk of malignancy. Survival is improving over time despite older age at diagnosis. Type of surgical resection and the addition of lymph node resection were not associated with OS.