INRG Staging System

INRGSS: International Neuroblastoma Risk Group Staging System

The INRGSS (International Neuroblastoma Risk Group Staging System), with two stages of localized (L1 and L2) – and two stages of metastatic disease (M and MS), was introduced in 2008. Unlike INSS, the INRGSS is a clinical classification system that is determined prior to any treatment, including surgery. The INRGSS is based on preoperative imaging, with attention paid to whether the primary tumor is affected by one or more of 20 specific Image Defined Risk Factors (Tables 1A and 1B). Neither the midline nor the lymph node status is included in the staging criteria. Metastatic disease is staged similarly in INRGSS and INSS with the important difference that the upper age limit of INRGSS stage MS is 18 months, whereas it is 12 months in INSS stage 4S. The INRGSS constitute one of seven factors included in the International Neuroblastoma Risk Group Pre-treatment Classification Schema.


Stage L1: Locoregional tumor without IDRFs
Stage L2: Locoregional tumor with one or more IDRFs
Stage M: Distant metastatic disease (except Ms)
Stage Ms: INRG Stage L1 or L2 tumor with metastatic disease confined to skin and/or liver and/or bone marrow



Please refer to Monclair T, Brodeur GM, Ambros PF, Brisse H, Cecchetto G, Holmes K, Kaneko M, London WB, Matthay KK, Nuchtern JG, von Schweinitz D, Cohn SL, and Pearson ADJ for the INRG Task Force. The International Neuroblastoma Risk Group (INRG) Staging System.
J. Clin. Oncol., 27:298-303, 2009 for further details.