Abstract
Receptors for the incretin glucagon-like peptide-1 (GLP-1R) have been found overexpressed in selected types of human tumors and may, therefore, play an increasingly important role in endocrine gastrointestinal tumor management. In particular, virtually all benign insulinomas express GLP-1R in high density. Targeting GLP-1R with indium-111, technetium-99m or gallium-68-labeled exendin-4 offers a new approach that permits the successful localization of small benign insulinomas. It is likely that this new non-invasive technique has the potential to replace the invasive localization of insulinomas by selective arterial stimulation and venous sampling. In contrast to benign insulinomas, malignant insulin-secreting neuroendocrine tumors express GLP-1R in only one-third of the cases, while they more often express the somatostatin subtype 2 receptors. Importantly, one of the two receptors appears to be always overexpressed. In special cases of endogenous hyperinsulinemic hypoglycemia (EHH), that is, in the context of MEN-1 or adult nesidioblastosis GLP-1R imaging is useful whereas in postprandial hypoglycemia in the context of bariatric surgery, GLP-1R imaging is probably not helpful. This review focuses on the potential use of GLP-1R imaging in the differential diagnosis of EHH.
Highlights
Insulinomas are rare, usually benign insulin-secreting neuroendocrine neoplasms (NEN) located in the pancreas (Service et al 1991, Placzkowski et al 2009)
The evidence level for direct comparison of glucagon-like peptide 1 receptor (GLP-1R) imaging and 18F-DOPA PET is scarce: we showed in a subpopulation of our latest prospective GLP-1R imaging study who received both PET/CT scans (5/52 patients) a better performance of 68Ga-DOTA-exendin-4 PET/CT compared to 18F-DOPA PET/CT without carbidopa (Antwi et al 2018)
In view of the often multiple pancreatic NENs visualized on conventional imaging in the context of multiple endocrine neoplasia type 1 (MEN-1) patients, the exact localization of the insulin-secreting PanNET is critical for the surgical strategy so as to avoid unnecessary morbidity due to too extensive surgery
Summary
Insulinomas are rare (incidence 1-4/Mio/year), usually benign insulin-secreting neuroendocrine neoplasms (NEN) located in the pancreas (Service et al 1991, Placzkowski et al 2009). On the other hand GLP-1R PET/CT with 68Ga-NODAGA-exendin-4 detected insulinomas with a much higher sensitivity than SSTR PET/CT (93.5 vs 61.3%) in a prospective comparison in 31 patients with biochemically proven hyperinsulinemic hypoglycemia (Boss et al 2019).
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