Functional imaging in phaeochromocytoma and neuroblastoma with 68 Ga-DOTA-Tyr 3 -octreotide positron emission tomography and 123 I-metaiodobenzylguanidine: a clarification

Purpose 68 Ga-DOTA-Tyr 3 -octreotide positron emission tomography ( 68 Ga-DOTA-TOC PET) has proven to be superior to 111 In-DTPA-D-Phe 1 -octreotide ( 111 In-octreotide) planar scintigraphy and SPECT imaging in neuroendocrine tumours (NETs). Because of these promising results, we compared the accuracy of 123 I-metaiodobenzylguanidine ( 123 I-MIBG) imaging with PET in the diagnosis and staging of metastatic phaeochromocytoma and neuroblastoma, referring to radiological imaging as reference standard. Methods Three male and eight female patients (age range 3 to 68 years) with biochemically and histologically proven disease were included in this study. Three male and three female patients were suffering from phaeochromocytoma, and five female patients from neuroblastoma. Comparative evaluation included morphological imaging with CT or MRI, functional imaging with 68 Ga-DOTA-TOC PET and 123 I-MIBG imaging. Imaging results were analysed on a per-patient and on a per-lesion basis. Results On a per-patient basis, both 68 Ga-DOTA-TOC and 123 I-MIBG showed a sensitivity of 100%, when compared with anatomical imaging. In phaeochromocytoma patients, on a per-lesion basis, the sensitivity of 68 Ga-DOTA-TOC was 91.7% and that of 123 I-MIBG was 63.3%. In neuroblastoma patients, on a per-lesion basis, the sensitivity of 68 Ga-DOTA-TOC was 97.2% and that of 123 I-MIBG was 90.7%. Overall, in this patient cohort, 68 Ga-DOTA-TOC PET identified 257 lesions, anatomical imaging identified 216 lesions, and 123 I-MIBG identified only 184 lesions. In this patient group, the overall sensitivity of 68 Ga-DOTA-TOC PET on a lesion basis was 94.4% (McNemar p <0.0001) and that of 123 I-MIBG was 76.9% (McNemar p <0.0001). Conclusion Our analysis in this relatively small patient cohort indicates that 68 Ga-DOTA-TOC PET may be superior to 123 I-MIBG gamma-scintigraphy and even to the reference CT/MRI technique in providing particularly valuable information for pretherapeutic staging of phaeochromocytoma and neuroblastoma.