Insulinoma-Accurate Preoperative Localization Is the Key to Management: An Initial Experience

Abstract

Insulinoma is the commonest functioning pancreatic neuroendocrine tumor. The only curative treatment is surgical excision after preoperative localization. A retrospective analysis of nine patients (February 2017-June 2020), 2 males and 7 females, was done for clinical presentation, biochemistry, localization methods, intraoperative findings, postoperative outcome, histopathology reports, and follow-up. Techniques for localization of the tumor were pancreatic protocol triple-phase multi-detector computed tomography (MDCT), endoscopic ultrasound (EUS), Ga 68 DOTANOC PET-CT, and Ga 68 NOTA-exendin-4 PET-CT (GLP1R scan). The mean age was 38 (range 20-68) years and mean duration of symptoms 34 (range 8-120) months, and symptoms of Whipple's triad were present in all cases after a supervised 72-h fast. MDCT localized tumor in 8/9 cases. EUS before MDCT in one patient had also localized tumors. Ga 68 DOTANOC PET-CT detected tumor in 2/4 patients. In one patient, MDCT or DOTANOC PET scan could not localize tumor; GLP1R scan localized tumor accurately. Two patients had associated MEN1 syndrome. All 9 patients underwent surgical resection (four open and five laparoscopic) of tumor-enucleation (3), distal pancreatectomy with splenectomy (3), and pancreatoduodenectomy (PD) (3). The last four procedures and all three enucleations were laparoscopic. Five patients developed postoperative pancreatic fistula (POPF), only one grade B which required percutaneous drain placement. One patient, who had initial open enucleation, developed hypoglycemia after 48 h; PD was performed. All patients were cured and all, except one (who died of upper GI bleed), were alive and disease-free during a mean follow-up of 26 (range 2-41) months. Preoperative localization of insulinoma is important and decides the outcome of surgery in terms of cure. MDCT can localize tumors in most patients; the last resort for localization is the GLP1R scan. Laparoscopic procedures are equally effective compared to open surgery. Considering the benign nature of the disease, enucleation is the procedure of choice.

Keywords: Enucleation; Ga 68 NOTA-exendin-4 PET-CT; Insulinoma; Pancreatic neuroendocrine tumor.

Fig. 1

Computed tomography images of patients of insulinoma. a Head. b Uncinate process. c Body. d Tail of the pancreas

Fig. 2

a MDCT image of insulinoma showing enhancing lesion in the tail of the pancreas mimicking as spleniculi. b GLP1R scan image of the same patient showing uptake in the lesion. c Enucleated specimen