Localization of Neuroendocrine Tumors Using Somatostatin Receptor Imaging With Indium-111-Pentetreotide (OctreoScan).

BACKGROUND: Many imaging methods have been used to detect neuroendocrine tumors of the gastrointestinal system. There is no gold standard for identifying the location of primary tumors and their potential metastases, and most conventional imaging techniques cannot detect tumors less than 1.0 cm in size. METHODS: The authors have investigated the use of 111-In-pentetreotide as an imaging agent for abdominal neuroendocrine tumors. RESULTS: The agent is cleared rapidly by the kidneys and is primarily excreted intact with a biologic half-life of six hours. The largest radiation burden is to the spleen and kidneys. A nine-center study conducted in Europe involved 365 patients with gastroenteropancreatic neuroendocrine tumors that were also imaged by other methods. The results of 111-In-pentetreotide were in agreement with those obtained by other methods for 79% of tumor locations. An additional 110 tumor localizations were detected that were not seen with conventional methods. The smallest gastrinoma imaged by 111-In-pentetreotide was a 4-mm duodenal tumor. CONCLUSIONS: Scintigraphy with 111-In-pentetreotide is effective in visualizing various somatostatin receptors characteristic of neuroendocrine tumors of the gastrointestinal tract. Insulinomas, however, are not well imaged. Concurrent computed tomography scanning is advised to minimize the risk of missing liver metastases.