Patterns of Recurrence after Resection for Pancreatic Neuroendocrine Tumors: Who, When, and Where?

Pancreatic neuroendocrine tumors (pan-NENs) represent an increasingly common indication for pancreatic resection, but there are few data regarding possible recurrence after surgery. The aim of the study was to describe the frequency, timing, and patterns of recurrence after resection for pan-NENs with consequent implications for postoperative follow-up.

We performed a retrospective analysis of pan-NENs resected between 1990 and 2015 at The Pancreas Institute, University of Verona Hospital Trust. Predictors of recurrence were assessed. Survival analysis was conducted using the Kaplan-Meier and conditional survival (CS) methods.

The cohort consisted of 487 patients with a median follow-up of 71 months. Recurrence developed in 12.3%: 54 (11.1%) liver metastases, 11 (2.3%) local recurrence, 10 (2.1%) nodal recurrence, and 8 (1.6%) metastases in other organs. Thirty-one (6.4%) died due to disease recurrence. Size > 21 mm, G3 grade, nodal metastasis, and vascular infiltration were independent predictors of overall recurrence. Recurrence occurred either during the first year of follow-up (n = 9), or after 10 years (n = 4). CS analysis revealed that nonfunctioning G1 pan-NEN ≤20 mm without nodal metastasis or vascular invasion had a negligible risk of developing recurrence. In the present series, after 5 years of follow-up without developing recurrence, tumor recurrence occurred only in the form of liver metastases.

Recurrence of pan-NENs is rare and is predicted by tumor size, nodal metastasis, grading, and vascular invasion. Patients with G1 pan-NEN without nodal metastasis and vascular invasion may be considered cured by surgery. After 5 years without recurrence, follow-up should focus on excluding the development of liver metastases.