The utility of metaiodobenzylguanidine (MIBG) scintigraphy in patients with pheochromocytoma

Background: Radiolabeled metaiodobenzylguanidine scintigraphy (MIBG) can be used to image pheochromocytomas. While cross-sectional imaging techniques such as computed tomography (CT) or magnetic resonance imaging (MRI) usually localize the tumor, MIBG is often obtained to rule out multifocal and metastatic disease, and to corroborate anatomic imaging with functional data. We questioned the utility of MIBG in the diagnosis and management of pheochromocytoma. Methods: All patients who received MIBG at one academic center from 1999 to 2004 were identified. For the subset of patients who received MIBG in the work-up of possible pheochromocytoma, the following data were reviewed: demographics, symptoms, results of biochemical and imaging studies, histopathological diagnosis, and management. Results: A total of 60 patients received MIBG, including 27 patients for the evaluation of a possible pheochromocytoma. Biochemical testing was performed in all patients. Fourteen patients received MIBG despite normal biochemistry and an absence of risk factors such as a hereditary syndrome or prior history of pheochromocytoma. None of these 14 low-risk patients with negative biochemistry had a final diagnosis of pheochromocytoma. In the ten patients with pheochromocytoma, all tumors were localized by CT and/or MRI. Importantly, MIBG did not identify any foci of disease not seen on cross sectional imaging, and MIBG did not alter the surgical management of any patient in this series. Conclusions: In patients with clinical findings suggestive of pheochromocytoma, biochemical testing should be used to confirm the diagnosis, and cross-sectional imaging is sufficient for tumor localization. In the absence of hereditary disease or a past history of pheochromocytoma, MIBG does not alter the treatment plan and therefore should not be routinely performed. Instead, MIBG should be used selectively, such as for the rare patient with a biochemical diagnosis of pheochromocytoma and no tumor seen on exhaustive anatomical imaging.