Comparative evaluation of iodine-131 metaiodobenzylguanidine and 18-fluorodeoxyglucose positron emission tomography in assessing neural crest tumors: Will they play a complementary role?

Abstract

Background:18-Fluorodeoxyglucose positron emission tomography (FDG-PET) has established a role in the evaluation of several malignancies. However, its precise clinical role in the neural crest cell tumors continues to evolve.Purpose:The purpose of this study was to compare iodine-131 metaiodobenzylguanidine (131I-MIBG) and FDG-PET of head to head in patients with neural crest tumors both qualitatively and semiquantitatively and to determine their clinical utility in disease status evaluation and further management.Materials and Methods:A total of 32 patients who had undergone 131I-MIBG and FDG-PET prospectively were evaluated and clinicopathologically grouped into three categories: neuroblastoma, pheochromocytoma, and medullary carcinoma thyroid.Results:In 18 patients of neuroblastoma, FDG PET and 131I-MIBG showed patient-specific sensitivity of 84% and 72%, respectively. The mean maximum standardized uptake value (SUVmax) of primary lesions in patients with unfavorable histology was found to be relatively higher than those with favorable histology (5.18 ± 2.38 vs. 3.21 ± 1.69). The mean SUVmaxof two common sites (posterior superior iliac spine [PSIS] and greater trochanter) was higher in patients with involved marrow than those with uninvolved one (2.36 and 2.75 vs. 1.26 and 1.34, respectively). The ratio of SUVmaxof the involved/contralateral normal sites was 2.16 ± 1.9. In equivocal bone marrow results, the uptake pattern with SUV estimation can depict metastatic involvement and help in redirecting the biopsy site. Among seven patients of pheochromocytoma, FDG-PET revealed 100% patient-specific sensitivity. FDG-PET detected more metastatic foci than 131I-MIBG (18 vs. 13 sites). In seven patients of medullary carcinoma thyroid, FDG-PET localized residual, recurrent, or metastatic disease with much higher sensitivity (32 metastatic foci with 72% patient specific sensitivity) than 131I-MIBG, trending along the higher serum calcitonin levels.Conclusions:FDG-PET is not only a good complementary modality in the management of neural crest cell tumors but also it can even be superior, especially in cases of 131I-MIBG nonavid tumors.