Rhabdomyosarcoma Stages and Risk Groups

Once rhabdomyosarcoma (RMS) has been diagnosed and the type of RMS identified, doctors need to assess how much cancer there is and where it has spread. This is known as the stage of the cancer. The stage is one of the most important factors in determining a person's prognosis (outlook). It's also important when deciding on the best treatment options.

Doctors use the results of imaging tests and biopsies and the examination of the organs during surgery to learn how far the cancer has spread. If there is any doubt about the extent of the cancer, more biopsies or other tests may be done.

RMS is staged differently from most other cancers. Doctors first determine 3 key pieces of information:

• The TNM stage
• The clinical group
• Whether the cancer cells have a PAX/FOX01 fusion gene

These factors are used to divide patients into risk groups, which then are used to guide treatment.

The stages and risk groups for RMS can be confusing. If you have any questions about the staging or risk groups, ask the doctor or nurse to explain it to you in a way you understand.

The TNM stage

The TNM stage is determined before treatment starts, and is based on 3 key pieces of information:

• T: The characteristics of the main tumor (location and size)
• N: Whether the cancer has spread to nearby lymph nodes (bean-sized collections of immune system cells)
• M: Whether the cancer has metastasized (spread) to distant parts of the body

These factors are combined to determine an overall stage:

Stage 1

The tumor started in a favorable area:

• The orbit (area around the eye)
• The head and neck area, except for parameningeal sites (areas next to the membranes covering the brain, such as the nasal passages and nearby sinuses, middle ear, and the uppermost part of the throat)
• A genital or urinary site, except the bladder or prostate gland
• Bile ducts (tubes leading from the liver to the intestines)

The tumor can be any size. It may have grown into nearby areas and/or spread to nearby lymph nodes, but it has not spread to distant parts of the body.

Stage 2

The tumor started in an unfavorable site:

• The bladder or prostate
• An arm or leg
• A parameningeal site (an area next to the membranes covering the brain, such as the nasal passages and nearby sinuses, middle ear, or the uppermost part of the throat)
• Any other part of the body not mentioned in stage 1

The tumor is no more than 5 cm (about 2 inches) across and there is no evidence that it has spread to nearby lymph nodes or distant parts of the body.

Stage 3

The tumor started in an unfavorable site:

• The bladder or prostate
• An arm or leg
• A parameningeal site (an area next to the membranes covering the brain, such as the nasal passages and nearby sinuses, middle ear, or the uppermost part of the throat)
• Any other part of the body not mentioned in stage 1

And one of the following applies:

• The tumor is no more than 5 cm across but has spread to nearby lymph nodes
• The tumor is larger than 5 cm across and may or may not have spread to nearby lymph nodes

In either case, the cancer has not spread to distant parts of the body.

Stage 4

The tumor can have started anywhere in the body and can be of any size. It has spread to distant parts of the body such as the lungs, liver, bones, or bone marrow.

Clinical group

The clinical group is based on the extent of the disease and how completely it is removed during initial surgery. The groups are defined as follows.

Group I

This group includes children with localized RMS (the cancer has not spread to nearby lymph nodes or to distant sites in the body) that is removed completely by surgery.

Group II

This group includes children with localized RMS, but in whom cancer cells have been found at the edges (margins) of the removed specimen (meaning that there may have been a small amount of cancer left behind).

It also includes children with RMS that has spread to the nearby lymph nodes.

Group III

These children have tumors that could not be removed completely. Some tumor was left behind that could be seen with the naked eye. The cancer may have spread to nearby lymph nodes, but there is no sign that it has spread to distant organs.

Group IV

At the time of diagnosis, these children have evidence of distant cancer spread to places such as the lungs, liver, bones, bone marrow, or to distant muscles or lymph nodes.

Risk groups

Using the information about the TNM stage, the clinical group, and the PAX/FOX01 fusion gene status, doctors divide patients into 3 risk groups. This helps doctors decide how aggressive treatment should be.

The risk groups are based on what has been learned from research on people previously treated for RMS. The groups discussed here are based on the most current information, but these may change in the future as safer and more effective treatments are developed.

Low-risk group

About 1 in 3 children with RMS falls into the low-risk group. It includes:

• Children with TNM stage 1 RMS that falls into clinical groups I, II, or III, and in which the cancer cells do not have a PAX/FOX01 fusion gene
• Children with stage 2 or 3 RMS who are in clinical groups I or II, and in which the cancer cells do not have a PAX/FOX01 fusion gene

Intermediate-risk group

About half of children of RMS fall into the intermediate-risk group. It includes:

• Children with stage 2 or 3 RMS who are in clinical group III, and in whom the cancer cells do not have a PAX/FOX01 fusion gene
• Children with RMS that has not spread to distant parts of the body (stage 1, 2, or 3), and in which the cancer cells do have a PAX/FOX01 fusion gene
• Children younger than 10 years of age with widespread (stage 4) RMS, in which the cancer cells do not have a PAX/FOX01 fusion gene

High-risk group

This group includes:

• Children 10 years of age or older with widespread (stage 4) RMS, in which the cancer cells do not have a PAX/FOX01 fusion gene
• Children with widespread (stage 4) RMS, in which the cancer cells do have a PAX/FOX01 fusion gene