Molecular imaging to the surgeons rescue: Gallium-68 DOTA-exendin-4 positron emission tomography-computed tomography in pre-operative localization of insulinomas

Abstract

Background:Insulinoma is an islet-cell neoplasm that secretes insulin. It is usually localized to the pancreas and is often the most common cause of endogenous hyperinsulinemic hypoglycaemia in non-diabetic adult patients. Surgical excision with a curative intent is the standard modality of treatment, and it requires precise localization of tumor tissue. Ga-68 DOTA-exendin-4 PET/CT scan is a clinically reasonable and sensitive scan for the identification of insulinoma. The aim of this prospective cohort study was to determine the overall accuracy of Ga-68 DOTA-exendin-4 PET/CT scan in the detection of insulinoma.Materials and Methods:Eight patients with fasting hyperinsulinemic hypoglycaemia with neuroglycopenic symptoms were enrolled in this study which was conducted during October 2016 to October 2017. Whole body PET/CT scan was performed on a Philips time of flight PET/CT scanner, 60 minutes after injection of Ga-68 DOTA-exendin-4 (and also Ga-68 DOTANOC). The imaging findings were compared to the histopathological diagnosis in six out of eight patients and to subsequent follow up in the remaining two patients who did not undergo surgery.Results:The sensitivity of Ga-68 DOTA-Exendin-4 PET/CT scan in insulinoma detection was found to be 75%.Conclusion:Ga-68 DOTA-Exendin-4 PET/CT scan is highly sensitive for identification and exact localization of insulinoma which can guide better surgical exploration. However, randomised controlled trials are needed to assess the accuracy of Ga-68 DOTA-Exendin PET/CT scan in localization of insulinoma.

Exendin‐4‐based imaging in insulinoma localization: Systematic review and meta‐analysis

“…15,16,21,29 As described previously, nesidioblastosis and islet cell hyperplasia can also present with TN results due to variable expression of GLP-1 R in these lesions and these cases cannot be differentiated from insulinoma on the clinical ground. 8,14,29 So, in such cases if responsive, medical management can be the best logical course. 15 In refractory cases, invasive techniques like SACST or EUS can be followed by exploration with intra-operative tumour palpation and US to rule out focal lesion before proceeding to near-total pancreatectomy.…”

“…In cases with small pancreatic tail lesions, the usual intense tracer uptake in the left kidney interferes with tumour visualization especially with the use of SPECT/CT. [14][15][16]18,21,23,24,26,29 To overcome this limitation, the use of PET/CT was suggested to provide higher spatial resolution to differentiate tumour and left renal tracer uptake. 8 Also delayed imaging allowing the renal tracer washout was utilized to enhance this contrast due to persistent tumour uptake.…”

“…16,29 The result is the inclusion of cases with these diagnoses in larger studies from tertiary care centres. 15,16,21,29 In these cases, TN reporting with exendin-4-based imaging was supplanted with other imaging modalities to raise doubt on the diagnosis of insulinoma. This was also seen in a few patients with NIPHS, congenital hyperinsulinism and pre-diabetes.…”

“…1 But MS due to surreptitious use of OHAs and IAH had been missed in some cases due to limited availability and detectability of SU screening assays and insulin autoantibody assay, respectively. 16,29 The result is the inclusion of cases with these diagnoses in larger studies from tertiary care centres. 15,16,21,29 In these cases, TN reporting with exendin-4-based imaging was supplanted with other imaging modalities to raise doubt on the diagnosis of insulinoma.…”

“…8 Exendin-4-based imaging has been shown to have higher sensitivity and specificity than conventional anatomic and other functional imaging. 8,16,21,29,31 With the increasing availability and use of this tracer for insulinoma localization, the clinicians need to be aware of the strengths and potential pitfalls of this imaging. The current IPD-MA was targeted to provide a comprehensive review of the published literature for exendin-4-based imaging.…”