Metaiodobenzylguanidine assessment of metastatic neuroblastoma: observer dependency and chemosensitivity evaluation....

In children over 1 year of age with metastatic neuroblastoma, clearance of metaiodobenzylguanidine (MIBG) skeletal uptake after four courses of induction chemotherapy is one of the most powerful prognostic factors. How subjective is quantification of MIBG uptake, and can earlier MIBG scintigraphy separate good and bad responders?

The data from 47 patients 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 score and the relative score (calculated by dividing the global score after two courses by the initial score) were compared to the final score. Good responders were those who scored 0 at final MIBG.

Between two observers, the correlation coefficient for the global score was superior to 0.80, in nine of ten comparisons established between observers 1-5. The initial score did not predict the final score insofar as only nine of fourteen patients with low initial scores were good responders. The relative score also failed to predict outcome; only six of ten patients with favorable relative score (i.e., <20%), were good responders.

This scoring system is reliable and may be used in multicentric trials. However, both initial and relative scores failed to predict final outcome. Thus, intermediate MIBG may be omitted during induction therapy assessment.