Intraoperative intermittently scanned continuous glucose monitoring in the management of patients with pancreatic insulinoma

Introduction: Insulinomas represent the most common functional pancreatic neuroendocrine tumors. Following preoperative localization, surgical excision is the curative treatment. It may be difficult to confirm a complete resection of insulinoma. We used intermittently scanned continuous glucose monitoring (isCGM) to record the fluctuation of interstitial glucose throughout surgery to help verify the tumor's complete surgical excision.

Materials and methods: In five individuals with insulinoma undergoing laparoscopic surgery we used the isCGM system (Freestyle Libre 2 Abbott) during tumor removal in order for the surgeon to understand "in real-time" the extent of tumor removal.

Results: Two patients received no preoperative treatment, while three patients received medical treatment with either lanreotide (2 patients) or diazoxide (1 patient). In the non-treated patients, following tumor resection, there was a rapid interstitial glucose increase along with stabilized glucose levels thoroughly documented by intraoperative isCGM. Lanreotide treatment, on the other hand, resulted in only a minor increase in interstitial glucose. Finally, diazoxide-treated patients had a response that was intermediate between lanreotide-treated and non-treated patients.

Conclusion: Our findings suggest that isCGM is a useful tool to monitor the outcome of surgery during pancreatic insulinoma excision, assisting the surgical team in successfully removing the tumor. Despite the limited sample size, the results are promising, and, if validated in larger studies, they make us believe that the use of CGM systems has a definite benefit for becoming a standard in the surgical treatment of insulinomas.