Bhatia KS et al. – Extra-adrenal and small adrenal pheochromocytomas are more likely to result in false negatives on [123I]MIBG; tumoral necrosis or hemorrhage do not consistently relate to [123I]MIBG uptake, although adrenal pheochromocytomas with minimal solid tissue due to extensive necrosis may predict a negative [123I]MIBG result Methods
Study of performance of [123I]MIBG and correlation with cross-sectional imaging in primary pheochromocytomas
Review of 76 pts with both pre-operative [123I]MIBG and cross-sectional imaging for confirmed primary pheochromocytoma: 60 adrenal tumors in 55 pts and 33 extra-adrenal tumors in 23 pts (2 pts had both adrenal and extra-adrenal tumors)
Pheochromocytoma metastases not evaluated
Results
Main outcome measure(s): [123I]MIBG studies independently reviewed and correlated with CT and MRI examinations and tumor functional status for features predicting a false negative [123I]MIBG result
Overall sensitivity of [123I]MIBG: 75%
Tumor detection lower for extra-adrenal (58%) vs adrenal (85%) pheochromocytomas
For extra-adrenal tumors, [123I]MIBG showed 8 /14 carotid body, 2/2 intra-thoracic, 8/14 retroperitoneal, and 2/3 pelvic pheochromocytomas
Overall, MRI showed 68/68 and CT 72/74 primary pheochromocytomas
Tumor size correlated with [123I]MIBG uptake for adrenal but not extra-adrenal tumors
When tumors were adjusted for size, no other imaging feature or functional status correlated with [123I]MIBG negativity
Large areas of necrosis or hemorrhage in 2 large [123I]MIBG-negative adrenal tumors
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