Eur J Nucl Med (1988) 14:337-340 European Nuc lear Journal of Medicine © Springer-Verlag 1988 Toxicity from treatment of neuroblastoma

Abstract. Toxic effects from 13 li_meta_iodobenzylguanidine (131I-MIBG) treatments of neuroblastoma in six patients were recorded. The toxicity was largely confined to the he-matologic system where circulating leukocytes and platelets regularly declined after each dose of 13q-MIBG; the values reached nadirs between three and seven weeks and recov-ered slowly over subsequent weeks. Prior bone marrow transplantation a d infiltration of bone marrow by neurob-lastoma appeared to make the hematologic system more vulnerable to the radiation. Dosimetry revealed greater ab-sorbed radiation by the whole body than by the blood and bone marrow. These observations are explained by a rela-tively rapid exit of 131I-MIBG from the blood to other tissues (but not to the bone marrow). Since treatment of an aggressive and lethal tumor such as neuroblastoma should be pushed to a degree of toxicity, careful dosimetry in each case will be necessary as a guide to reach the point of maximally tolerable toxicity