Primary hypothyroidism as a consequence of 131-I-metaiodobenzylguanidine treatment for children with neuroblastoma

Background. 131-I-metaiodobenzylguanidine is a radioiodinated compound selectively concentrated by cells of neuroectodermal origin, including neuroblastoma cells, for this reason it may represent a promising treatment modality for neuroblastoma in childhood. Although a potential side effect of 131-I-MIBG administration is thyroid dysfunction, relatively few data are reported about this issue. Methods. A series of 14 long term surviving patients with neuroblastoma who had been treated with 131-I-MIBG courses ranging from 2.5 to 5.5 gigabecquerels after surgical and conventional pharmacologic therapy is reported. Results. Twelve patients developed primary hypothyroidism that was clinically overt in 8 patients and compensated in 4 patients within 6-12 months of completion of 131-I-MIBG administration. Only in two patients was thyroid function spared. Significant correlations between the cumulative dose of 131-I-MIBG and the degree of thyroid failure were not found. Conclusions. Primary hypothyroidism appears to be a common side effect in children with neuroblastoma treated with 131-I-MIBG. This finding suggests that methods to preserve thyroid function other than oral administration of iodide should be sought.