PURPOSE:
A collaborative effort was undertaken to derive an internationally agreed semi-quantitative meta-iodobenzylguanidine (mIBG) scoring method in neuroblastoma by harmonising previously established scoring systems, which were each found to have prognostic value at the end of induction (Yanik JNM 2013). The aim of this analysis was to investigate the individual effect on event-free-survival (EFS) of the two components of the scoring system: 1) the number of involved anatomic regions and 2) the scoring value within each segment and to evaluate the prognostic value of the new proposed scoring system.
PATIENTS AND METHODS:
COG and SIOPEN merged data of children with stage 4, mIBG avid, neuroblastoma entered on the COG-A3973 (216pts) and the SIOPEN/HR-NBL1 trial (341 pts). Two independent nuclear medicine review teams scored mIBG scans pre- and post-induction according to Curie- and SIOPEN-methodologies. Here, the SIOPEN score evaluating the skeletal (mIBG) uptake on a 0-6 scale in 12 anatomical regions was chosen for the statistical analysis due to the greater range of values. The two study cohorts were investigated separately and a bootstrap-based internal validation was performed.
RESULTS
In 557 pts the cumulative SIOPEN-score post induction had a significant impact on EFS with 5-years EFS of 41%, 33% and 15% for total scores of 0, 1-3 and >3, respectively. However, no increasing hazards with increasing scores per segment were observed. In contrast, the number of positive segments alone had a highly significant impact on EFS with 5-year EFS of 41%, 32% and 14% for patients with 0,1-2 and >2 positive segments post induction.
CONCLUSION
The number of positive segments was the most important prognostic factor. Weighting the involvement within segments did not improve the prognostic value of the scoring system. These results suggest a possible simplification of MIBG scoring, facilitating future international collaborations.