Diagnosis of pheochromocytoma using [123I]-compared with [131I]-metaiodobenzylguanidine scintigraphy

Background: Patient with pheochromocytoma (PCT) cannot be cured without operation, therefore, preoperative determination of the localization of PCT should be performed accurately. [I-131]-Metaiodobenzylguanidine (MIBG) scintigraphy is a gold standard for the diagnosis of PCT. However, [I-123]MIBG is also found to accumulate in PCT. In order to clarify the usefulness of [I-123]-MIBG scintigraphy for the local detection of PCT, we compared the distribution of [I-123]- and [I-131]-MIBG in patients with or without PCT. Methods: [I-131]- and [I-123]-MIBG scintigraphy was performed in 29 and 16 patients, respectively. In the former group, 14 patients had PCT, 12 had hypertension without any adrenal disorder and three had other diseases. In the latter group, eight patients had PCT, two had hypertension without any adrenal disorder and six had other diseases. The sensitivity, specificity and accuracy of [I-123]-compared with [I-131]-MIBG scintigraphy were compared. Results: The sensitivity of [I-131]- and [I-123]-MIBG scintigraphy was 85.7 and 90%, respectively. The specificity of each test was 100%. The accuracy of [I-131]- and [I-123]-MIBG scintigraphy was 93.1 and 95%, respectively. The quality of images obtained using [I-123]-MIBG was better than with [I-131]-MIBG, because [I-123]-MIBG generated a higher dose of gamma-rays with a higher specificity than [I-131]-MIBG. In addition, normal adrenal grands were visualized in 50% of patients tested with [I-123]-MIBG scintigraphy. Conclusions: These results indicate that [I-123]-MIBG scintigraphy is a valuable tool for the local detection of PCT, as is [I-131]-MIBG scintigraphy. Furthermore, it is possible that [I-123]-MIBG can be used as an alternative to [I-131]-MIBG for the detection of PCT. Our study was not a prospective study and the background of the patients was not matched. Further prospective studies are needed in order to determine the efficacy of [I-123]MIBG scintigraphy for the diagnosis of PCT.