Nuclear medicine in the detection and management of pancreatic islet-cell tumours

Over the last decade somatostatin receptor scintigraphy using various derivatives of long-acting somatostatin analogues has gained its place in the management of pancreatic islet-cell tumours. Scintigraphy is based on the high-affinity binding of such somatostatin analogues to receptors over-expressed by these tumour types. Following the introduction of 111In-DTPA-D-Phe1-octreotide, clinical studies with radiolabelled DOTA-Tyr3-octreotide and DOTA-Tyr3-octreotate derivatives have shown considerable improvement of imaging results with increased tumour uptake. One of the newer developments, 68Ga-labelled DOTA-Tyr3-octreotide, has shown promising results in patients with pancreatic islet-cell tumours, based on the high-affinity binding to the somatostatin receptor subtype 2 in combination with positron emission tomography (PET) technology. Other peptides-such as ligands for the gastrin/CCK2 receptors or vasoactive intestinal peptide (VIP)-have also been studied for imaging pancreatic cell tumours. Whereas small-sized gastrinoma, somatostatinoma, glucagonoma, carcinoid and VIPoma are frequently detected by somatostatin receptor scintigraphy, insulinoma may escape detection due to reduced receptor expression. Following peptide receptor scintigraphy, a change in patient management is reported in up to 30% of patients. When labelled with 90Y or 177Lu, some somatostatin analogues have been applied to patients in advanced stages of the disease. Despite positive response data in 50% of patients, long-term results and survival rates are lacking.