Biodistribution of post‐therapeutic versus diagnostic 131I‐MIBG scans in children with neuroblastoma

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Abstract
Background To evaluate the biodistribution of therapeutic 131I-metaiodobenzylguanidine (MIBG) and assess the sensitivity of diagnostic versus therapeutic 131I-MIBG scans to detect metastatic disease. Procedure This retrospective study included 44 diagnostic and post-therapy scans (PTS) in 18 children with neuroblastoma treated with 131I-MIBG (2.0–33.1 GBq). The findings of diagnostic scans (DS) (2.6–44.4 MBq) were compared to those of corresponding PTS. Results In terms of biodistribution, the PTS identified 131I-MIBG activity in one or more patients in the following regions not detected on the DS: nasal mucosa, cerebellum, central brain, adrenals, spleen, kidneys, thyroid, salivary glands, lower halves of the lungs, bladder, bowel, and an incisional scar. Conversely, the DS identified activity in the thorax, heart, kidneys, and bladder each in one patient without being visualized on the PTS. In terms of sensitivity to detect metastatic disease, 210 lesions were seen on the PTS compared to 151 on the DS. The PTS demonstrated sites of disease not evident in the DS in 16 cases. Conclusions The biodistribution of 131I-MIBG is different using therapeutic doses as compared to pre-therapy doses. 131I-MIBG imaging following high therapeutic doses often reveals sites of occult metastatic disease that may be clinically relevant.