Meta-[123I]iodobenzylguanidine single photon emission computed tomography in chemodectomas.

Chemodectoma is a rare, slow growing neoplasm with local aggressiveness and a high rate of residuals after surgery, arising from paraganglionic tissue (neural crest) and therefore able to take up Metaiodobenzylguanidine (MIBG). The aim of this study was to evaluate the diagnostic accuracy of 123I-MIBG Single Photon Emission Computed Tomography (SPECT) in comparison to Selective Digital Angiography (SDA), Computed Tomography (CT) and Magnetic Resonance Imaging (MRI). We studied 50 patients (41 women, 9 men) mean age 56 years (range 14-79), with diagnostic suspicion of chemodectoma (CH). There were 2 groups of patients: Group A (26 patients) examined before Surgery and Group B (24 patients) examined after surgery. SPECT of the head and neck region was performed 4 hours after i.v. administration of 185 MBq of 123I-MIBG. All patients were pre-treated with iodine solution. We performed a qualitative evaluation of the reconstructed slices. In Group A, all patients with CH (24) showed accumulation of MIBG in agreement with SDA, CT and MRI: 2 patients (histologically one had a cordoma, the other metastasis of papillary thyroid carcinoma), did not show any accumulation of 123I-MIBG. In Group B, 6 patients showed accumulation of 123I-MIBG in local residuals, and 9 were negative. Six patients with a lesion smaller than 1.5 cm were negative. Three patients had a positive scan but no lesion on SDA, CT and MRI. 123I-MIBG SPECT proved to be useful procedure in the diagnosis of untreated CH. During follow-up after surgery this procedure may assume a role in the perspective of radiometabolic therapy with 131I-MIBG.