Enucleation for sporadic non-functioning pancreatic neuroendocrine tumors larger than 2 centimeters is associated with equivalent morbidity and survival compared to smaller tumors: a multi-institutional study

Introduction: Non-functioning pancreatic neuroendocrine tumor (NF-PanNET) ≤ 2 cm can be observed or resected. Surgery remains recommended for NF-PanNET > 2 cm but its extent, enucleation (EN) versus formal resection, remains controversial. Methods: Multicentric retrospective cohort of sporadic NF-PanNET patients treated with EN. Short and long-term outcomes were compared according to tumor size on imaging ≤ 2 cm vs > 2 cm. Results: 131patients underwent EN for NF-PanNET, including 103 (79.0%) ≤ 2 cm and 28 (21.0%) > 2 cm (extremes, 4–55 mm). Patients’ characteristics were comparable, and tumor characteristics only differed in their diameter. Clavien III-IV complications were similar (18.4% vs 17.9%, p= 1.00) with one death in NF-PanNET ≤ 2cm. Grade B/C pancreatic fistula were comparable (16.5% vs 10.7%, p= 0.850). In NF-PanNET > 2cm there were more pT2/3 stage tumors (85.7% vs 21.4%, p<0.001), similar rates of grade G2/3 tumors (25% vs 16.5%, p= 0.408) with a median Ki67 of 2 (IQR: 1–3), and of lymphovascular and perineural invasions. Lymph node picking was done in 46 (35.1%) patients, with a higher median number of harvested lymph nodes in NF-PanNET > 2 cm (4 vs 3, p= 0.01). All were pN0. R0 resection rate (78.6% vs 82.5%, respectively; p= 0.670) was equivalent. Five-year overall (100% vs 99%, p= 0.602) and 10-year disease-free (96% vs 92%, respectively; p= 0.532) survivals were comparable. Conclusions: EN for selected NF-PanNET > 2 cm carries equivalent morbidity, overall and disease-free survivals compared to those observed with NF-PanNET ≤ 2 cm.