Controversy: asymptomatic small pancreatic neuroendocrine neoplasms : Current standards in diagnostics and treatment

Background: For the increasingly diagnosed entity of small asymptomatic, sporadic, nonfunctional, pancreatic neuroendocrine neoplasms (pNEN), a negligible or at least unclear prognostic relevance of the disease for patient survival has often been observed.

Objective: Safety and acceptance of a watch-and-wait strategy versus surgical resection for small, asymptomatic nonfunctional (NF) pNEN.

Methods: Presentation and evaluation of the relevant literature as well as the corresponding national and European guidelines.

Results: Surgery of small NF-pNEN shows complication rates of 15-32% (Clavien-Dindo ≥ 3) and a mortality of 3.6%. Even for pNEN < 2 cm the presence of lymph node metastases has been observed in 11% of cases, while their prognostic relevance in G1-pNEN compared with active surveillance remains unclear. On average 14% of patients under active surveillance for small NF-pNEN, underwent a resection. Relevant tumor growth during surveillance was found in < 20% of cases. In all well-selected surveillance cohorts no metachronous lymphatic or distant metastases occurred during active surveillance and especially no cases of a metachronous no longer curable disease.

Conclusions: Even small asymptomatic NF-pNEN have a certain metastatic potential but the clinical relevance has prospectively not yet been clearly determined. Controlled surveillance of these tumors is at least an alternative to immediate tumor resection. Especially patients above 70 years old do not seem to benefit from resection. The pros and cons of a resection should therefore be individually evaluated with the patient.