Background: Metaiodobenzylguanidine (mIBG) is a guanethidine analog that has demonstrated a high sensitivity and specificity in detecting bone metastases in about 90% of metastatic neuroblastomas. However, the predictive value of initial mIBG scan in neuroblastoma patients older than 1 year of age regarding response to initial chemotherapy has yet to be ascertained. Therefore, a scoring system for grading the positivity of mIBG scans was devised and applied in a retrospective study in an attempt to determine whether this score had a prognostic value in neuroblastoma patients older than 1 year of age at diagnosis.
Methods: Eighty-six children, older than 1 year of age, with metastatic neuroblastomas were homogeneously treated and had a mIBG scan performed at diagnosis and following the induction regimen to assess bone metastases. Each mIBG scan was assigned a reproducible score and the predictive value of the initial mIBG score was assessed in order to evaluate response to induction regimen.
Results: The relative risk of failing to achieve complete remission after four courses of induction therapy was 6.9 times higher in patients who had more than four mIBG spots at diagnosis. A multivariate analysis including the established prognostic factors revealed that the initial mIBG score was the only significant factor (P < 0.001).
Conclusions: The initial mIBG scan is of prognostic significance to predict response to chemotherapy for metastatic neuroblastoma in children older than 1 year of age. A prospective study comparing this initial mIBG score with other recently established prognostic factors is warranted.