EFFECT OF SPECIFIC ACTIVITY ON NEUROBLASTOMA UPTAKE OF I-123 METAIODOBENZYLGUANIDINE IN NUDE-MICE XENOGRAFTED WITH SK-N-SH CELLS

The effect of specific activity of meta[I-123]iodobenzylguanidine ([I- 123]MIBG) on neuroblastoma uptake was studied in a nude mouse model (N MRI nu/nu) xenografted subcutaneously with SK-N-SH cells. Groups of ei ght animals received [I-123]MIBG intravenously with a specific activit y of greater than or equal to 260 GBq/mu mol (no-carrier-added), 3.7 G Bq/mu mol, 37 MBq/mu mol, and 0.37 MBq/mu mol, respectively. All anima ls in the group injected with 0.37 MBq/mu mol died immediately after t he injection. Al 4 and 24 h, there was no significant effect of specif ic activity on tumor uptake of [I-123]MIBG in the different groups. Th e uptake of non-tumor tissue was in general lower with 37 MBq/mu mol c ompared to higher specific activities. The differences in blood, heart , liver, spleen and lungs were statistically significant at 24 h, wher eas at 4 h significant differences were only present in the heart, liv er and lungs. The results suggest that for the treatment of children w ith neuroblastoma a lower specific activity of radioiodinated MIBG may minimize the radiation exposure to non-tumor tissue but not to the tu mor. Higher mass of MIBG >0.5 mu mol/g, however, is considered as leth al dose in our nude mice model and corresponding doses may cause toxic side effects in human.