# The International Neuroblastoma Risk Group (INRG) staging system: an INRG Task Force report — GCMD Library
Tom Monclair, Garrett M Brodeur, Peter F Ambros, Hervé J Brisse, Giovanni Cecchetto, Keith Holmes, Michio Kaneko, Wendy B London, Katherine K Matthay, Jed G Nuchtern, Dietrich von Schweinitz, Thorsten Simon, Susan L Cohn, Andrew D J Pearson; INRG Task Force
Purpose: 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).
Conclusion: 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.
Type: video · 0 min · posted 2026-03-24
Canonical: https://library.globalcastmd.com/watch/the-international-neuroblastoma-risk-group-staging-system-an-inrg-task-force-report-11727
## Chapters
- [0:00](https://library.globalcastmd.com/watch/the-international-neuroblastoma-risk-group-staging-system-an-inrg-task-force-report-11727?t=0) Image-Defined Risk Factors in Neuroblastoma
## Statements
- "IDRFs are necessary knowledge for clinicians treating neuroblastoma to determine safety of surgical intervention" — Sophia Schermerhorn (clinical) [0:00](https://library.globalcastmd.com/watch/the-international-neuroblastoma-risk-group-staging-system-an-inrg-task-force-report-11727?t=0)
- "IDRFs are imaging findings on CT or MRI that predict when neuroblastoma may be difficult or dangerous to remove surgically" — Sophia Schermerhorn (clinical) [0:14](https://library.globalcastmd.com/watch/the-international-neuroblastoma-risk-group-staging-system-an-inrg-task-force-report-11727?t=14)
- "The IDRF concept was first introduced in 2009 by the International Neuroblastoma Risk Group" — Sophia Schermerhorn (guideline) [0:21](https://library.globalcastmd.com/watch/the-international-neuroblastoma-risk-group-staging-system-an-inrg-task-force-report-11727?t=21)
- "The International Neuroblastoma Risk Group defined 20 specific imaging risk factors" — Sophia Schermerhorn (guideline) [0:21](https://library.globalcastmd.com/watch/the-international-neuroblastoma-risk-group-staging-system-an-inrg-task-force-report-11727?t=21)
- "Most IDRFs relate to how the tumor interacts with critical anatomy" — Sophia Schermerhorn (clinical) [0:29](https://library.globalcastmd.com/watch/the-international-neuroblastoma-risk-group-staging-system-an-inrg-task-force-report-11727?t=29)
- "In the abdomen, a tumor that infiltrates the portahepati or hepatoduodenal ligament is considered to contain an IDRF" — Sophia Schermerhorn (clinical) [0:34](https://library.globalcastmd.com/watch/the-international-neuroblastoma-risk-group-staging-system-an-inrg-task-force-report-11727?t=34)
- "The presence of an IDRF does not mean a tumor cannot be resected" — Sophia Schermerhorn (clinical) [0:41](https://library.globalcastmd.com/watch/the-international-neuroblastoma-risk-group-staging-system-an-inrg-task-force-report-11727?t=41)
- "IDRF presence signals that surgery may be technically more complex" — Sophia Schermerhorn (clinical) [0:41](https://library.globalcastmd.com/watch/the-international-neuroblastoma-risk-group-staging-system-an-inrg-task-force-report-11727?t=41)
- "Patients with IDRFs often receive neoadjuvant therapy first to try to shrink the tumor" — Sophia Schermerhorn (clinical) [0:41](https://library.globalcastmd.com/watch/the-international-neuroblastoma-risk-group-staging-system-an-inrg-task-force-report-11727?t=41)
- "Surgeons use IDRFs to predict surgical risk and guide the safest treatment approach using imaging" — Sophia Schermerhorn (clinical) [0:52](https://library.globalcastmd.com/watch/the-international-neuroblastoma-risk-group-staging-system-an-inrg-task-force-report-11727?t=52)
## Transcript
If you're someone who treats neuroblastoma, you need to know about IDRFs to know whether it's safe to go to the operating room. Hi, I'm Dr. Sophia Skermhorn, a research fellow at Cincinnati Children's, and today I'm going to explain image-defined risk factors, also known as IDRFs. IDRFs are imaging findings on CT or MRIs that predict when a neuroblastoma may be difficult or dangerous to remove surgically. The concept was first introduced in 2009 by the International Neuroblastoma Risk Group, which defined 20 specific imaging risk factors shown. Here, most IDRFs relate to how the tumor interacts with critical anatomy. For example, in the abdomen, a tumor that infiltrates the portahepati or hepatoduodenal ligament would be considered to contain an IDRF. The presence of an IDRF doesn't mean that a tumor can't be resected, but it does signal that the surgery may be technically more complex, and patients often receive neoadjuvant therapy first to try to shrink the tumor. So when surgeons talk about IDRFs, what they're really doing is using imaging to predict surgical risk and guide the safest treatment approach.
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