The International Neuroblastoma Risk Group (INRG) staging system: an INRG Task Force report.
OBJECTIVE
The International Neuroblastoma Risk Group (INRG) classification system was developed to establish a consensus approach for pretreatment risk stratification. Because the International Neuroblastoma Staging System (INSS) is a postsurgical staging system, a new clinical staging system was required for the INRG pretreatment risk classification system.


METHODS
To stage patients before any treatment, the INRG Task Force, consisting of neuroblastoma experts from Australia/New Zealand, China, Europe, Japan, and North America, developed a new INRG staging system (INRGSS) based on clinical criteria and image-defined risk factors (IDRFs). To investigate the impact of IDRFs on outcome, survival analyses were performed on 661 European patients with INSS stages 1, 2, or 3 disease for whom IDRFs were known.


RESULTS
In the INGRSS, locoregional tumors are staged L1 or L2 based on the absence or presence of one or more of 20 IDRFs, respectively. Metastatic tumors are defined as stage M, except for stage MS, in which metastases are confined to the skin, liver, and/or bone marrow in children younger than 18 months of age. Within the 661-patient cohort, IDRFs were present (ie, stage L2) in 21% of patients with stage 1, 45% of patients with stage 2, and 94% of patients with stage 3 disease. Patients with INRGSS stage L2 disease had significantly lower 5-year event-free survival than those with INRGSS stage L1 disease (78% +/- 4% v 90% +/- 3%; P = .0010).


CONCLUSIONS
Use of the new staging (INRGSS) and risk classification (INRG) of neuroblastoma will greatly facilitate the comparison of risk-based clinical trials conducted in different regions of the world.
Monclair
Tom
T
Section for Paediatric Surgery, Division of Surgery, Rikshospitalet University Hospital, NO-0027 Oslo, Norway. tom.monclair@rikshospitalet.no
Brodeur
Garrett M
GM
Ambros
Peter F
PF
Brisse
Hervé J
HJ
Cecchetto
Giovanni
G
Holmes
Keith
K
Kaneko
Michio
M
London
Wendy B
WB
Matthay
Katherine K
KK
Nuchtern
Jed G
JG
von Schweinitz
Dietrich
D
Simon
Thorsten
T
Cohn
Susan L
SL
Pearson
Andrew D J
AD
D002648:Child; D018572:Disease-Free Survival; D006801:Humans; D038801:International Classification of Diseases; D008279:Magnetic Resonance Imaging; D009367:Neoplasm Staging; D009447:Neuroblastoma / Q000145:classification / Q000000981:diagnostic imaging / Q000473:pathology*; D012307:Risk Factors; D015996:Survival Rate; D014057:Tomography, X-Ray Computed