Update on the development of the international neuroblastoma risk group (INRG) classification schema

Abstract

9503 Background: Modern treatment strategies for neuroblastoma (NB) are tailored according to patient risk. However, it is not currently possible to compare the results of clinical studies conducted around the globe because the criteria used to define risk are not uniform. A committee of international investigators with expertise in NB have worked during the past 2 years to develop a uniform International NB Risk Group (INRG) Classification System for pre-treatment stratification. Methods: Investigators from North America and Australia (COG); Europe (SIOPEN and Germany), and Japan collated data on 8,800 children with NB diagnosed between 1990 and 2002. Survival tree regression analyses tested 13 potential prognostic factors. Tumor differentiation, MKI, and diagnostic category were evaluated individually in lieu of the International NB Pathology Classification (INPC) system to determine if these histologic features had prognostic value independent from age. To stage patients at the time of diagnosis prior to surgery, a new staging system was developed (INRGSS) based on the presence or absence of image-defined risk factors (IDRFs) and metastases. Results: Since statistical analyses demonstrated support for an optimal age cut- off between 14–19 months, 18 months was selected. In addition to age, stage, MYCN amplification, tumor differentiation, ploidy, and genetic aberrations of 11q were found to be the most highly prognostically significant factors. These clinical and biological factors were combined to define 15 INRG pre-treatment groups. Patients with low- (3 groups), intermediate- (4 groups), high- (4 groups), or ultra-high-risk NB (4 groups) had EFS of ≥85%, >70–85%, >50–70%, or <50%, respectively. Conclusion: International collaborative studies in NB will be greatly facilitated by the INRG classification system which will allow comparisons of different risk-based therapeutic approaches in homogeneous patient cohorts. No significant financial relationships to disclose.