Prognosis of sporadic resected small (≤2 cm) nonfunctional pancreatic neuroendocrine tumors - a multi-institutional study.

Background: Malignant potential of small (≤20 mm) nonfunctional pancreatic neuroendocrine tumors (sNF-PNET) is difficult to predict and management remain controversial. The aim of this study was to assess the prognosis of sporadic nonmetastatic sNF-PNETs.

Methods: Patients were identified from databases of 16 centers. Outcomes and risk factors for recurrence were identified by uni- and multivariate analyses.

Results: sNF-PNET was resected in 210 patients, and 66% (n = 138) were asymptomatic. Median age was 60 years, median tumor size was 15 mm, parenchyma-sparing surgery was performed in 42%. Postoperative mortality was 0.5% (n = 1), severe morbidity rate was 14.3% (n = 30), and 14 of 132 patients (10.6%) with harvested lymph nodes had metastatic lymph nodes. Tumor size, presence of biliary or pancreatic duct dilatation, and WHO grade 2-3 were independently associated with recurrence. Patients with tumors sized ≤10 mm were disease free at last follow-up. The 1-, 3- and 5-year disease-free survival rates for patients with tumors sized 11-20 mm on preoperative imaging were 95.1%, 91.0%, and 87.3%, respectively.

Conclusions: In sNF-PNETs, the presence of biliary or pancreatic duct dilatation or WHO grade 2-3 advocate for surgical treatment. In the remaining patients, a wait-and-see policy might be considered.