Iodine-131 metaiodobenzylguanidine scintigraphy of carcinoid tumors

Iodine-131 metaiodobenzylguanidine ([131I]MIBG) is concentrated in pheochromocytomas and can be detected by external imaging. We administered [131I]MIBG to 23 patients with carcinoid tumors to determine if it would be useful in scanning patients with these tumors. The carcinoid tumors of 14 of the 23 patients (61%) were visualized. Iodine-131 MIBG was concentrated most avidly by tumors of midgut origin (ileum, cecum); it was concentrated less avidly by some tumors of foregut origin (pancreas, stomach); it was not significantly concentrated by other tumors of foregut origin (bronchus). We conclude that 131I is a useful imaging agent for carcinoid tumors.