Impact of Tumor Size and Location on Endoscopic Ultrasound-Guided Sampling of Pancreatic Neuroendocrine Tumors: A Recursive Partitioning Analysis.

Background: Current guidelines provide weak recommendations to treat small (< 2 cm) non-functional pancreatic neuroendocrine tumors with low Ki-67 proliferation index either by resection or clinical follow-up. However, there is a lack of consensus regarding the minimal size of pNET, which allows EUS-guided biopsy with high enough diagnostic accuracy for stratification. Methods: We conducted a retrospective, bicentric analysis of patients who had undergone EUS-guided pNET sampling in two tertiary care Endoscopy Units in Germany and Poland. Using a recursive parti-tioning of the tree-aided model, we aimed to stratify the probability of successful EUS-guided biopsy of pNET lesions according to their size and location. Results: In our pNET cohort, successful histological confirmation of a pNET diagnosis was achieved in 59/ 69 (85.5%) cases at the initial EUS-guided biopsy. In 41 patients with a pNET size less than 18.5 mm, the EUS-guided first biopsy was successful in 90.2%. In 16 of these patients with smaller lesions, EUS-guided sampling was 100% in very small (less than 11 mm) and extremely small lesions (less than 8 mm). The biopsy success rate was 100% in tail lesions in the size range between > 5.95 and < 8.1 mm but only 33.3% independent of the investigator in pancreatic head or body, with an error rate of 11.2% Conclusion: Using a recursive partitioning of the tree-aided stratification model, we demonstrate for the first time that in balancing risks and benefits, very small pNETs (< 1 cm) in the tail of the pancreas should be sampled under EUS-guidance. (c) 2022 IAP and EPC. Published by Elsevier B.V. All rights reserved.