From the Research
Extendin-4 imaging, specifically 68Ga-NODAGA-exendin-4 PET/CT, is the recommended imaging modality for localizing insulinomas due to its high sensitivity and specificity, as demonstrated in the most recent study 1.
Key Points:
- Extendin-4 imaging uses radiolabeled exendin-4, a glucagon-like peptide-1 (GLP-1) receptor agonist, to visualize tissues expressing GLP-1 receptors, particularly pancreatic beta cells and insulinomas.
- The most common form is 68Ga-DOTA-exendin-4 PET/CT imaging, but 68Ga-NODAGA-exendin-4 PET/CT has shown superior diagnostic accuracy in a prospective multicenter study 1.
- This technique provides high sensitivity and specificity for detecting insulinomas and other neuroendocrine tumors that express GLP-1 receptors, with detection rates exceeding 90% in many studies.
- Patients should fast for 4-6 hours before the procedure and discontinue GLP-1 receptor medications for at least 48 hours prior to avoid receptor competition.
- The imaging works because exendin-4 binds with high affinity to GLP-1 receptors that are overexpressed on insulinoma cells and beta cells, allowing for their visualization when the molecule is tagged with a radioactive isotope.
- Side effects are minimal but may include transient hypoglycemia in insulinoma patients due to the partial agonist effect on insulin secretion.
Comparison with Other Imaging Modalities:
- 68Ga-NODAGA-exendin-4 PET/CT has been shown to be superior to other imaging modalities, including 68Ga-DOTA-somatostatin analog (DOTA-SSA) PET/CT, contrast-enhanced CT/contrast-enhanced diffusion-weighted imaging-MRI, and endoscopic ultrasound, in terms of diagnostic accuracy 1.
- Exendin-4-based imaging has also been compared to 18F-DOPA PET/CT in the detection of focal congenital hyperinsulinism, with 68Ga-NODAGA-exendin-4 PET/CT showing higher sensitivity and better interobserver correlation 2.
Clinical Implications:
- The use of 68Ga-NODAGA-exendin-4 PET/CT can improve the detection and localization of insulinomas, allowing for more accurate diagnosis and treatment.
- This imaging modality can be particularly useful in patients with suspected insulinomas who have negative or inconclusive results on conventional imaging studies.
- As with any imaging modality, it is essential to weigh the benefits and risks of 68Ga-NODAGA-exendin-4 PET/CT and to use it judiciously, taking into account the patient's individual clinical situation and medical history.