Ga-68-DOTA-Exendin-4 reliably detects insulinomas and shows regional differences in pancreatic distribution

Ziel/Aim:

Insulinomas are predominantly benign neuroendocrine tumors originating from beta cells within islets of Langerhans of the endocrine pancreas. Autonomous insulin secretion by insulinomas is the most prevalent cause for endogenous hyperinsulinaemic hypoglycaemia. Since surgical resection represents the only curative therapy for these patients, exact tumor localization and discrimination of insulinomas from focal or diffuse manifestations of nesidioblastosis is crucial for optimal treatment strategies. We investigated the diagnostic value of PET imaging of the glucagon-like peptide-1 (GLP-1) receptor, which is overexpressed in high density in insulinomas.

Methodik/Methods:

In 10 Patients with clinically and biochemically suspected insulinoma, PET/CT was performed 124 ± 8 min after injection of 84 ± 21 MBq of Ga-68-DOTA-Exendin-4. In addition to the identification of focal tracer uptake, in vivo biodistribution (SUV_MEAN) was assessed with focus on intrapancreatic regional tracer uptake (i.e. head, body and tail). Imaging results were correlated with histopathological findings, if patients underwent resection.

Ergebnisse/Results:

Increased focal Ga-68-DOTA-Exendin-4 uptake (ÆSUV_MAX 23.9 ± 7.8) was observed in 8/10 patients. 7 patients with focal uptake underwent surgery with tumor enucleation and histopathological proof of insulinoma (7/7). In one patient with focal uptake, no histopathological proof was available as the severely compromised clinical condition prohibited surgery. 2/10 patients showed no focal uptake, and were thus considered to suffer from diffuse nesidioblastosis, and consequently received medical treatment. Although regional physiological distribution of Ga-68-DOTA-Exendin-4 showed significant differences (p < 0.001; ANOVA) with higher uptake in the head and tail region as compared to the pancreatic body (p < 0.05; t-test), no difference was seen in comparison to patients with suspected nesidioblastosis.

Schlussfolgerungen/Conclusions:

Ga-68-DOTA-Exendin-4 reliably detected insulinomas as confirmed in all patients undergoing surgery subsequently to focal tracer uptake. In contrast, diffuse parenchymal uptake in 2 patients with nesidioblastosis seems to be comparable to uptake of regular pancreatic tissue.