Imaging neuroblastoma: what the radiologist needs to know

Neuroblastoma is the most common extracranial solid malignancy in children. The tumor has variable biological behavior that can be predicted by patient age, genetic features, tumor biology and extent of disease at diagnosis. Factors chosen by various cooperative groups to define risk of treatment failure have been non-uniform. Therefore, historically, it has been difficult to compare outcomes across clinical trials performed around the world. This has hindered the advancement of treatment strategies to improve survival of these patients. The International Neuroblastoma Risk Group (INRG) was established in 2004 to develop a consensus approach to pretreatment risk stratification. The result was the development of the INRG Staging System (INRGSS) which relies on imaging-defined risk factors (IDRFs) that are determined before surgery or other therapy. With the application of the INRGSS the radiologist's role in staging children with neuroblastoma is increased. This review provides an overview of the INRGSS and the IDRFs.