Comparison of Iodobenzylguanidine Imaging with Computed Tomography in Locating Pheochromocytoma*

Abstract

Ninety-nine patients suspected of having pheochromocytoma were studied with [131I]metaiodobenzylguanidine scintigraphy, and 92 of them were studied with computed tomography (CT). In 49 patients, the diagnosis was ruled out; in 3 patients, it remained doubtful; and in 47 patients, it was confirmed. Two patients had tumors that did not secrete epinephrine or norepinephrine, and 45 had secreting pheochromocytomas. In these latter patients, there were 4 false negative [131I]metaiodobenzylguanidine scans, all intraadrenal tumors, and 4 false negative CT scans, 3 extraadrenal and 1 intraadrenal tumors. For about 80% of the patients and/or the tumor sites, both methods were thus in agreement. They were complementary in the remaining 20%. The advantage of scintigraphy is to screen the whole body with high specificity and to locate extra-adrenal sites or metastases of pheochromocytoma with better accuracy than CT. The limits of scintigraphy are the possibility of false negative scans in around 10% of patients, whereas CT visualizes more than 95% of intraadrenal tumors.