Rhabdomyosarcoma

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Early Detection, Diagnosis, and Staging TOPICS

How is rhabdomyosarcoma staged?

Once rhabdomyosarcoma (RMS) has been diagnosed and the type of RMS identified, doctors need to assess, as accurately as possible, how much cancer there is and where it has spread. The answers to these questions are expressed in a standard kind of shorthand known as staging.

The prognosis (outlook) for people with cancer depends, to a large extent, on the cancer’s stage. The stage of a cancer is one of the most important factors in choosing treatment.

Your child’s doctors will use the results of the imaging tests and biopsies (described in “How is rhabdomyosarcoma diagnosed?”) and the direct 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 may be done on tissues at the edge of the tumor, nearby lymph nodes, and any suspicious lumps in other parts of the body.

To stage RMS, doctors first determine 3 key pieces of information:

  • The type of RMS (embryonal or alveolar)
  • The TNM stage
  • The clinical group

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

RMS is staged differently from most other cancers, and it 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 it 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 5 cm (about 2 inches) or smaller 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 5 cm across or smaller 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.

About 10% to 15% of RMS patients are in group I.

Group II

This group includes children who have had all of the visible cancer removed by surgery, but 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), in the nearby lymph nodes, or in both places. In all cases, as much of the cancer has been removed as possible.

About 20% of RMS patients are in group II.

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.

About 50% of RMS patients are in group III.

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.

About 15% to 20% of RMS patients are in group IV.

Risk groups

Using the information about the type of RMS, the TNM stage, and the clinical group, doctors classify patients into 3 risk groups. Information about risk groups helps doctors decide how aggressive treatment should be.

The risk groups are based on what has been learned from previous research on patients’ outcomes. 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 embryonal rhabdomyosarcomas (ERMS) that fall into clinical groups I, II, or III
  • Children with stage 2 or 3 ERMS who are in clinical groups I or II

Intermediate-risk group

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

  • Children with stage 2 or 3 ERMS who are in clinical group III
  • Children with alveolar rhabdomyosarcoma (ARMS) that has not spread to distant parts of the body (stage 1, 2, or 3)

High-risk group

This group includes:

  • Children with widespread (stage 4) RMS (ERMS or ARMS)

Last Medical Review: 11/20/2014
Last Revised: 11/21/2014