Metaiodobenzylguanidine assessment of metastatic neuroblastoma: Observer dependency and chemosensitivity evaluation

Background. In children over 1 year of age with metastatic neuroblastoma, c learance of metaiodobenzylguanidine (MIBG) skeletal uptake after four cours es of induction chemotherapy is one of the most powerful prognostic factors . How subjective is quantification of MIBG uptake, and can earlier MIBG sci ntigraphy separate good and bad responders? Procedure. The data from 47 pat ients who received uniform induction therapy were reviewed. A novel scoring system of MIBG update intensity was proposed. Initial, intermediate (after two courses), and final (after four courses) intensities were scored (0 to 21 points) independently by six different observers. The initial global sc ore and the relative score (calculated by dividing the global score after t wo courses by the initial score) were compared to the final score. Good res ponders were those who scored 0 at final MIBG. Results. Between two observe rs, the correlation coefficient for the global score was superior to 0.80, in nine of ten comparisons established between observers 1-5. The initial s core did not predict the final score insofar as only nine of fourteen patie nts with low initial scores were good responders. The relative score also f ailed to predict outcome; only six of ten patients with favorable relative score (i.e., <20%), were good responders. Conclusions. This scoring system is reliable and may be used in multicentric trials. However, both initial a nd relative scores failed to predict final outcome. Thus, intermediate MIBG may be omitted during induction therapy assessment. (C) 2000 Wiley-Liss, I nc.