Scintigraphic imaging of carcinoid tumors

131-1-metaiodobenzylguanidine (131-1-MIBG) is used for scintigraphic localization and treatment of pheochromocytoma and neuroblastoma. Several other tumors, deriving from neuroectoderm (APUD tumors) may also produce catecholamines. 4 patients with surgically proven carcinoid tumors were studied by 131-1-MIBG scintigraphy. Scintigraphic images were performed with a computer assisted gamma camera 2.24, 48 and 72 hours after IV injection of 26 MBq 131-I-MIBG. In one patient single photon emission computed tomography (SPECT) with 185 Mgq 123-I-MIBG was performed additionally. Catecholamines were determined in 24-hours-urinary samples by HPLC. Serotonine was determined in plasma. Catecholamine excretion was normal in all patients, whereas serotonine was elevated in all of them. In 2 of 4 patients slight tracer uptake was observed in some of liver metastases, whereas other metastases in the liver and the primary tumor did not show 131-1-MIBG uptake. In one patient with a carcinoid tumor of the pancreas 131-1-MIBG scintigraphy and SPECT with 123-1-MIBG was positive. In one patient scintigraphy was false negative. MIBG scintigraphy is not only suitable for imaging pheochromocytoma and neuroblastoma, but may also localize carcinoid tumors and their metastases.