Comparing diagnostic performance of 131I-metaiodobenzylguanidine (131I-MIBG) and 99mTc-hydrazinonicotinyl-Tyr3-Octreotide (99mTc-HYNIC-TOC) in diagnosis and localization of pheochromocytoma and neuroblastoma

Introduction: The present study was aimed to assess the diagnostic performance of the two imaging methods of 131I-metaiodobenzylguanidine (131I-MIBG) and 99mTc-hydrazinonicotinyl-Tyr3-Octreotide (99mTc-HYNIC-TOC) in diagnosis and localization of pheochromocytoma and neuroblastoma. Methods: This study was conducted on 40 consecutive patients with positive pathological results for pheochromocytoma or neuroblastoma. The patients underwent both I-131 131I-MIBG and octreotide scintigraphies. By using the findings of cytopathology, biomarkers, imaging studies, as well as the results of a six-month follow-up, a composite reference standard (CRS) was defined as the diagnostic gold standard. Results:Overall comparison of these two agents revealed higher sensitivity for 131I-MIBG than octreotide study both in patient-based analysis (100% vs. 80.9%, respectively), and lesion-based analysis (94.4% vs. 80.56%, respectively). In pheochromocytoma 131I-MIBG and octreotide are both highly sensitive (100%), while 131I-MIBG is more specific (100% vs. 87.5%). In neuroblastoma, 131I-MIBG is more sensitive than octreotide (100% vs. 81.25%). Conclusion: Our study shows superiority of 131I-MIBG over octreotide scanning in detection of both neuroblastoma and pheochromocytoma lesions. However, a combination of these two diagnostic tools provides more complete information on the nature and the site of lesions. The first suggested study is 131I-MIBG scanning, and if it is not available, or detecting precise location of all lesions is of concern, octreotide scanning can be helpful as a complementary study.  Furthermore, in case of octreotide positive lesions, follow-up can be performed with octreotide scan with less radiation burden.