Somatostatin Receptor Scintigraphy in Localization of Pancreatic Neuroendocrine Tumors: A Preliminary Study

Objective: To study the ability of somatostatin receptor scintigraphy using Tc-99m-hydrazinonicotinyl-Tyr3-octreotide (Tc-99m-HYNIC-TOC) for localization of pancreatic neuroendocrine tumors. Methods: Five patients (3 female, 2 male; age range: 53 to 80 years; mean age: 65 years) with either histologically proven or clinically suspected insulinoma were studied. Ten mCi of Tc-99m-HYNIC-TOC were intravenously injected. Whole body scans were obtained 2 and 4 hours after injection. SPECT/CT studies of areas of interest were performed after the 4-hour whole body image. Scintigraphic findings were correlated not only with the results of conventional imaging methods, including computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound but also through 1-year clinical follow-up. Results: The Tc-99m-HYNIC-TOC study showed true-negatives in two patients suspected of insulinoma proven by intraoperative ultrasound in one case and 1-year clinical follow-up with no evidence of hypoglycemia in the other patient. Abnormal Tc-99m-HYNIC-TOC accumulation was demonstrated in three patients with pancreatic tumors. Additional metastatic lesions to lung and bone were detected in one patient formerly diagnosed of malignant insulinoma with multiple liver metastases. Conclusion: Tc-99m-HYNIC-TOC SPECT/CT imaging may provide more accurate staging of pancreatic neuroendocrine tumors than conventional imaging. It is an optional technique to recruit patients for somatostatin analogs therapy.