PURPOSE: Neuroblastoma may be treated with molecular radiotherapy, 131I 
meta-Iodobenzylguanidine and 177Lu Lutetium DOTATATE, directed at distinct 
molecular targets: Noradrenaline Transporter Molecule (NAT) and Somatostatin 
Receptor (SSTR2), respectively. This study used immunohistochemistry to evaluate 
target expression in archival neuroblastoma tissue, to determine whether it 
might facilitate clinical use of molecular radiotherapy.
METHODS: Tissue bank samples of formalin fixed paraffin embedded neuroblastoma 
tissue from patients for whom clinical outcome data were available were 
sectioned and stained with haematoxylin and eosin, and monoclonal antibodies 
directed against NAT and SSTR2. Sections were examined blinded to clinical 
information and scored for the percentage and intensity of tumour cells stained. 
These data were analysed in conjunction with clinical data.
RESULTS: Tissue from 75 patients was examined. Target expression scores varied 
widely between patients: NAT median 45%, inter-quartile range 25% - 65%; and 
SSTR2 median 55%, interquartile range 30% - 80%; and in some cases heterogeneity 
of expression between different parts of a tumour was observed. A weak positive 
correlation was observed between the expression scores of the different targets: 
correlation coefficient = 0.23, p = 0.05. MYCN amplified tumours had lower SSTR2 
scores: mean difference 23% confidence interval 8% - 39%, p < 0.01. Survival did 
not differ by scores.
CONCLUSIONS: As expression of both targets is variable and heterogeneous, 
imaging assessment of both may yield more clinical information than either 
alone. The clinical value of immunohistochemical assessment of target expression 
requires prospective evaluation. Variable target expression within a patient may 
contribute to treatment failure.