OBSERVATIONAL STUDY OF NATURAL HISTORY OF SMALL SPORADIC NONFUNCTIONING PANCREATIC NEUROENDOCRINE TUMORS

Introduction: Asymptomatic sporadic non-functioning well-differentiated pancreatic neuroendocrine tumors (NF-PNET) are increasingly diagnosed, and their management is controversial because of their overall good but heterogeneous prognosis. Objective: To assess the natural history of asymptomatic sporadic NF-PNETs smaller than 2 cm in size and the risk-benefit balance of non-operative management. Methods: From January 2000 to June 2011, 46 patients with proven AS-NF-PNET smaller than 2 cm in size were followed-up for at least 18 months with serial imaging in tertiary referral centers. Results: Patients were mainly female (65%), with a median age of 60 years. Tumors were mainly located in the pancreatic head (52%), with a median lesion size of 13 mm (9 –15). After a median follow-up of 34 months (24 –52) and an average of 4 (3– 6) serial imaging sessions, distant or nodal metastases appeared on the imaging in none of the patients. In 6 (13%) patients, a 20% increase in size was observed. Overall median tumor growth was 0.12 mm per year and neither patients nor tumor characteristics were found to be significant predictors of tumor growth. Overall, 8 patients (17%) underwent surgery after a median time from initial evaluation of 41 months (27–58); all resected lesions were ENETS T stage 1 (n=7) or 2 (n=1), grade 1, node negative, with neither vascular nor peripancreatic fat invasion. Conclusions: In selected patients, non-operative management of asymptomatic sporadic NF-PNET smaller than 2 cm in size is safe. Larger and prospective multicentric studies with long-term follow-up are now needed to validate this “wait and see” policy.