Background: Methods: Results: Conclusion:

Background: The prognostic impact of segmental chromosome alterations (SCAs) in children older than 1 year, diagnosed with localised unresectable neuroblastoma (NB) without MYCN amplification enrolled in the European Unresectable Neuroblastoma (EUNB) protocol is still to be clarified, while, for other group of patients, the presence of SCAs is associated with poor prognosis. Methods: To understand the role of SCAs we performed multilocus/pangenomic analysis of 98 tumour samples from patients enrolled in the EUNB protocol. Results: Age at diagnosis was categorised into two groups using 18 months as the age cutoff. Significant difference in the presence of SCAs was seen in tumours of patients between 12 and 18 months and over 18 months of age at diagnosis, respectively (P=0.04). A significant correlation (P=0.03) was observed between number of SCAs per tumour and age. Event-free (EFS) and overall survival (OS) were calculated in both age groups, according to both the presence and number of SCAs. In older patients, a poorer survival was associated with the presence of SCAs (EFS=46% vs 75%, P=0.023; OS=66.8% vs 100%, P=0.003). Moreover, OS of older patients inversely correlated with number of SCAs (P=0.002). Finally, SCAs provided additional prognostic information beyond histoprognosis, as their presence was associated with poorer OS in patients over 18 months with unfavourable International Neuroblastoma Pathology Classification (INPC) histopathology (P=0.018). Conclusions: The presence of SCAs is a negative prognostic marker that impairs outcome of patients over the age of 18 months with localised unresectable NB without MYCN amplification, especially when more than one SCA is present. Moreover, in older patients with unfavourable INPC tumour histoprognosis, the presence of SCAs significantly affects OS.

Purpose: Precise and comprehensive analysis of neuroblastoma genetics is essential for accurate risk evaluation and only pangenomic/multilocus approaches fulfill the present-day requirements. We present the establishment and validation of the PCR-based multiplex ligation-dependent probe amplification (MLPA) technique for neuroblastoma. Experimental Design: A neuroblastoma-specific MLPA kit was designed by the SIOP Europe Neuroblastoma Biology Committee in cooperation with MRC-Holland. The contained target sequences cover 19 chromosomal arms and reference loci. Validation was performed by single locus and pangenomic techniques (n = 174). Dilution experiments for determination of minimal tumor cell percentage were performed and testing of reproducibility was checked by interlaboratory testing (n = 15). Further 156 neuroblastomas were used for establishing the amplification cutoff level. Results: The MLPA technique was tested in 310 neuroblastomas and 8 neuroblastoma cell lines (including validation and amplification cutoff level testing). Intertechnique validation showed a high concordance rate (99.5%). Interlaboratory MLPA testing (κ = 0.95, P < 0.01) revealed 7 discrepant of 1,490 results (0.5%). Validation by pangenomic techniques showed a single discordance of 190 consensus results (0.5%). The test results led to formulation of interpretation standards and to a kit revision. The minimal tumor cell percentage was fixed at 60%. Conclusions: The recently designed neuroblastoma-specific MLPA kit covers all chromosomal regions demanded by the International Neuroblastoma Risk Group for therapy stratification and includes all hitherto described genetic loci of prognostic interest for future studies and can be modified or extended at any time. Moreover, the technique is cost effective, reliable, and robust with a high interlaboratory and intertechnique concordance. Clin Cancer Res; 17(4); 792–804. ©2011 AACR.