Observational study of natural history of small sporadic nonfunctioning pancreatic neuroendocrine tumors

Abstract

Context: Asymptomatic sporadic nonfunctioning, well-differentiated pancreatic neuroendocrine tumors (NF-PNETs) are increasingly diagnosed, and their management is controversial because of their overall good but heterogeneous prognosis. Objective: The objective of the study was to assess the natural history of asymptomatic sporadic NF-PNETs smaller than 2 cm in size and the risk-benefit balance of nonoperative management. Experimental Design: From January 2000 to June 2011, 46 patients with proven asymptomatic sporadic NF-PNETs smaller than 2 cm in size were followed up for at least 18 months with serial imaging in tertiary referral centers. Results: Patientsweremainlyfemale(65%),withamedianageof60years.Tumorsweremainlylocated in the pancreatic head (52%), with a median lesion size of 13 mm (range 9-15). After a median follow-up of 34 months (range 24-52) and an average of four (range 3-6) serial imaging sessions, distant or nodal metastases appeared on the imaging in none of the patients. In six patients (13%), a 20%or greater increase in sizewasobserved. Overall median tumor growthwas0.12mmper year,and neither patients nor tumor characteristics were found to be significant predictors of tumor growth. Overall, eight patients (17%) underwent surgery after a median time from initial evaluation of 41 months(range 27-58); all resected lesionswereEuropeanNeuroendocrineTumorSocietyTstage1(n=7) or 2 (n = 1), grade 1, node negative, with neither vascular nor peripancreatic fat invasion. Conclusions: In selected patients, nonoperative management of asymptomatic sporadic NF-PNETs smaller than 2 cmin size is safe. Larger and prospective multicentric studies with long-term follow-up are now needed to validate this wait-and-see policy. © 2013 by The Endocrine Society.