ACTIVITY OF I-123 METAIODOBENZYLGUANIDINE IN CHILDHOOD NEUROBLASTOMA - LACK OF RELATION TO TUMOR DIFFERENTIATION IN-VIVO

Neuroblastoma (NB) tumour cells have a remarkable tendency to differen tiate spontaneously or under the influence of certain drugs. it is not clear whether metaiodobenzylguanidine, (MIBG) uptake correlates with differentiation of NE cells, In 28 tumours of 26 patients, iodine-123 MIBG uptake in primary NBs was studied in relation to tumour different iation, tumour size, cell density and degree of necrosis in subsequent ly resected specimens, Genetic features such as the presence of chromo somal aberrations (1p-deletion and MYCN amplification) and/or P-glycop rotein (mdr-1 gene product) were also evaluated in relation to MIBG up take, A highly variable and unpredictable intensity of MIBG uptake was observed in primary as well as secondary resected tumours. This inten sity did not relate to any of the above-mentioned factors except that there was a trend towards more intense uptake with increasing size of the tumour, We conclude from our observations that, in contrast to com monly held opinion, well-differentiated tumours do not a priori show a lower MIBG uptake in vivo, even when there are a low number of viable cells and a high degree of necrosis. The degree of differentiation or tumour viability and necrosis following longstanding chemotherapeutic treatment cannot be predicted by the MIBG scan findings, The observed MIBG uptake may be importantly influenced by factors other than those associated with cellular differentiation.