Neuroblastoma Risk Groups

Children’s Oncology Group (COG) risk groups

The Children’s Oncology Group (COG) uses the major prognostic factors discussed in the staging section, combined with the INSS stage of the disease, to place children into 3 different risk groups: low, intermediate, and high. These risk groups are used to help predict how likely it is that a child can be cured. For example, a child in a low-risk group can often be cured with limited treatment, such as surgery alone. With children in higher risk groups, the chance of cure is not as great, so more intensive treatment is often needed.

These risk groups are based on what is now known about neuroblastoma and how it is treated. As new research provides more information, these risk groups may change over time. For example, in recent treatment recommendations the age cut-off for some of these categories has been revised from up to 12 months (365 days) to up to 18 months (547 days).

Low risk

• All children who are Stage 1
• Any child who is Stage 2A or 2B and younger than age 1
• Any child who is Stage 2A or 2B, older than age 1, whose cancer has no extra copies of the MYCN gene
• Any child who is Stage 4S (younger than age 1), whose cancer has favorable histology, is hyperdiploid (excess DNA) and has no extra copies of the MYCN gene

Intermediate risk

• Any child who is Stage 3, younger than age 1, whose cancer has no extra copies of the MYCN gene
• Any child who is Stage 3, older than age 1, whose cancer has no extra copies of the MYCN gene and has favorable histology (appearance under the microscope)
• Any child who is Stage 4, younger than age 1, whose cancer has no extra copies of the MYCN gene
• Any child who is Stage 4S (younger than age 1), whose cancer has no extra copies of the MYCN gene and has normal DNA ploidy (number of chromosomes) and/or has unfavorable histology

High risk

• Any child who is Stage 2A or 2B, older than age 1, whose cancer has extra copies of the MYCN gene
• Any child who is Stage 3, younger than age 1, whose cancer has extra copies of the MYCN gene
• Any child who is Stage 3, older than age 1, whose cancer has extra copies of the MYCN gene
• Any child who is Stage 3, older than 18 months of age, whose cancer has unfavorable histology
• Any child who is Stage 4, whose cancer has extra copies of the MYCN gene regardless of age
• Any child who is Stage 4 and older than 18 months
• Any child who is Stage 4 and between 12 and 18 months old whose cancer has extra copies of the MYCN gene, unfavorable histology, and/or normal DNA ploidy (a DNA index of 1)
• Any child who is Stage 4S (younger than age 1), whose cancer has extra copies of the MYCN gene

International Neuroblastoma Risk Group (INRG) classification

As with the staging system described in the previous section, a newer risk group classification system, the International Neuroblastoma Risk Group (INRG) classification, is now being studied and may soon replace the COG system above. This system is based on the newer INRGSS staging system, which includes the image-defined risk factors (IDRFs), as well as many of the prognostic factors listed in the staging section, such as:

• The child’s age
• Tumor histology (how the tumor looks under the microscope)
• The presence or absence of MYCN gene amplification
• Certain changes in chromosome 11 (known as an 11q aberration)
• DNA ploidy (the total number of chromosomes in the tumor cells)

The INRG classification uses these factors to put children into 16 different pre-treatment groups (lettered A through R). Each of these pretreatment groups falls into 1 of 4 overall risk groups:

• Very low risk
• Low risk
• Intermediate risk
• High risk

This system has not yet been widely adopted, but it is being researched in new treatment protocols.