[I-123]metaiodobenzylguanidine and [In-111]octreotide uptake in benign andmalignant pheochromocytomas

Selecting the appropriate approach for resection and follow-up of pheochrom ocytomas (PCCs) is highly dependent upon reliable localization and exclusio n of multifocal, bilateral, or metastatic disease. Metaiodobenzylguanidine (MIBG) scintigraphy was developed for functional localization of catecholam ine-secreting tissues. Somatostatin receptor imaging (SRI) has a high sensi tivity for localizing head and neck paragangliomas, but studies of intraabd ominal PCCs are rare. In this study we review our experience of [I-123]MIBG and SRI, performed since 1983 and 1989, respectively, in the work-up of pr imary and recurrent PCCs. Scintigraphic results were correlated with catech olamine secretion, size and site, malignancy, associated tumor syndromes, a nd morphological features. [I-123]MIBG scans were performed in a total of 75 patients, in 70 cases bef ore resection of primary PCCs and in 5 cases because of recurrent disease. Ninety-one PCCs were resected. The overall detection rates were 83.3% and 8 9.8% for PCCs larger than 1.0 cm. Multifocal disease was detected in 4 pati ents with [I-123]MIBG. [I-123]MIBG uptake correlated with greater size of P CC (r = 0.33; P = 0.008) and greater concentration of plasma epinephrine (r = 0.32; P = 0.006). [I-123]MIBG-negative PCCs (n = 14) had significantly ( P = 0.01) smaller diameters than [I-123]MIBG-positive tumors. Furthermore, [I-123]MIBG uptake was significantly higher in unilateral (P = 0.02), benig n (P = 0.02), sporadic (P = 0.02), intraadrenal (P = 0.02), and capsular in vasive (P = 0.03) PCCs than in bilateral, malignant, MEN2A/2B-related, extr aadrenal, and noninvasive PCCs, respectively. The detection rate of SRI was only 25% (8 of 32) for primary benign PCCs. In 14 patients metastases occu rred, which were effectively visualized with [I-123]MIBG in 8 of 14 cases. SRI was able to detect metastases in 7 of 8 cases, including 3 [I-123]MIBG- negative metastatic cases. In addition, [I-123]MIBG and SRI detected 2 recu rrences. In conclusion, [I-123]MIBG uptake is correlated with the size, epinephrine production, and site of PCCs. Its role in bilateral and MEN2A/2B-related PC Cs seems limited. In cases of recurrent elevation of catecholamines, locali zation of metastases and/or recurrence should be attempted with [I-123]MIBG scintigraphy. In suspicious metastatic PCCs, SRI might be considered to su pplement [I-123]MIBG scintigraphy.