Site-based performance of (131)I-MIBG imaging and (99m)Tc-HYNIC-TOC scintigraphy in the detection of nonmetastatic extra-adrenal paraganglioma

This study aimed to evaluate the performance of (131)I-metaiodobenzylguanidine (MIBG) imaging to detect nonmetastatic extra-adrenal paragangliomas at their respective sites (abdominal vs. thoracic vs. head and neck vs. urinary bladder), and compare it with that of (99m)Tc-hydrazinonicotinyl-tyr3-octreotide (HYNIC-TOC) scintigraphy. METHODS: We retrospectively analyzed 235 patients with nonmetastatic extra-adrenal paragangliomas who underwent preoperative (131)I-MIBG imaging or (99m)Tc-HYNIC-TOC scintigraphy. Of all 235 patients, 145 patients underwent both imaging procedures, 16 patients (131)I-MIBG imaging only and 74 patients (99m)Tc-HYNIC-TOC scintigraphy only. RESULTS: The overall sensitivity of (131)I-MIBG and (99m)Tc-HYNIC-TOC imaging to detect extra-adrenal paragangliomas regardless of tumor sites was 75.8% (122/161) and 67.6% (148/219), respectively (P = 0.082). However, when stratified by tumor sites, (131)I-MIBG imaging showed a significant improvement in the detection of extra-adrenal abdominal paragangliomas with a sensitivity of 90.3% (103/114), which was significantly higher than that of (99m)Tc-HYNIC-TOC scintigraphy (67.6% (96/142); P = 0.000). In addition, the intensity of tracer uptake in the extra-adrenal abdominal paragangliomas with (131)I-MIBG imaging was evidently higher than with (99m)Tc-HYNIC-TOC scintigraphy. The sensitivity of (131)I-MIBG imaging and (99m)Tc-HYNIC-TOC scintigraphy to detect urinary bladder, head and neck, and thoracic paragangliomas were 18.7 vs. 18.5% (P = 1.000); 17.4% vs. 84.6% (P = 0.000) and 60% vs. 94.4% (P = 0.030), respectively. CONCLUSIONS: (131)I-MIBG imaging could become the first-line investigation modality in patients with extra-adrenal abdominal paragangliomas. However, (99m)Tc-HYNIC-TOC scintigraphy has high sensitivity and is superior to (131)I-MIBG imaging for detecting head & neck and thoracic paraganglioma. Both (131)I-MIBG imaging and (99m)Tc-HYNIC-TOC scintigraphy have poor performance for detecting urinary bladder paragangliomas.