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The management of small nonfunctional pancreatic neuroendocrine tumors: It's time to define the high‐risk features

To the Editor, We read with great interest the article by Arra et al. The authors compared the long‐term outcomes of surgical resection and active surveillance for patients with small nonfunctional pancreatic neuroendocrine tumors (NF‐PNETs) and found that both approaches seem to be safe and feasible. We appreciate the authors' work in providing evidence of conservative management for small NF‐PNETs with a low risk of malignancy. However, we would like to raise the following comments. Small NF‐PNETs are a heterogeneous subset of tumors with controversy regarding their optimal management. Results from some surgical reports found that small NF‐PNETs had an unpredictable clinical course, and a subset of them may show aggressive behavior, for which surgery is recommended. However, due to the significant risks of complications of pancreatic surgery, conservative management for small NF‐PNETs has been recently proposed as a possible option. Several meta‐analyses and retrospective studies have shown that a surveillance approach can be safely applied to selective patients with small asymptomatic NF‐PNETs. In our opinion, currently, the main conundrum is not to evaluate the feasibility of conservative management, but to weigh the metastatic potential against the complications. Patients with a high risk of malignancy are obviously not good candidates for observation. Therefore, preoperative clinical features that can be used to predict aggressive behavior of small NF‐PNETs are urgently needed High tumor grade, tumor size >1.5 cm and tumor location in the body/tail has been considered to be high‐risk features of small NF‐PNETs. However, some of these studies were from public databases without information regarding the preoperative imaging and postoperative pathology reports. Because of the development of imaging technology, preoperative imaging features may now be used to evaluate the malignancy of small NF‐PNETs. As shown in the present study, patients with main pancreatic duct or biliary tree dilation and pancreatic trophy, which have been demonstrated as malignant imaging features, were also excluded from the analysis. Nevertheless, more high‐quality studies are needed to explore more imaging features for predicting the aggressive behavior of small NF‐PNETs In addition, we also have some concerns about this study. First, organ preserving surgery including distal pancreatectomy with splenic preservation, central pancreatectomy, and enucleation accounted for 24.3% (10/41) in the present study, which is a relatively low proportion compared with the study by Sallinen et al. (89/210, 42.4%). Second, in the surgical group, there were no node‐positive patients. We would like to know the proportion of patients who underwent lymphadenectomy, and how the authors evaluated indications for lymphadenectomy. Third, the median follow‐up time of the active surveillance and surgical group was 38.6 and 46.4 months, a relatively short time for such an indolent tumor Overall, we agree with the author that well‐differentiated PNETS with 2.0 cm or less and without a high risk of malignancy could undergo an active surveillance approach. More importantly, it's time to define the high‐risk features of small NF‐PENTs