Rhabdomyosarcoma Stages and Risk Groups
Once rhabdomyosarcoma (RMS) has been confirmed 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.
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.
Stage is one of the main factors in determining a person's risk group. Risk groups help doctors identify a person’s best treatment options and understand their prognosis (outlook). Risk groups in RMS are different from most other cancers and are based on what has been learned about RMS from clinical trials mostly in children. Doctors need 3 key pieces of information to decide on the best treatment plan:
- The TNM stage
- The clinical group
- Whether the cancer cells have a PAX/FOXO1 fusion gene
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 assigned 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 the cancer stage:
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
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.
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)
- Bile ducts (tubes leading from the liver to the intestines)
- 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.
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)
- Bile ducts (tubes leading from the liver to the intestines)
- 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.
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, bone marrow, or cerebrospinal fluid (CSF).
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:
This group includes people 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.
This group includes people 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 after surgery).
It also includes people with RMS that has spread to the nearby lymph nodes.
These people have tumors that could not be removed completely or were only biopsied. 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.
At the time of diagnosis, these people have evidence of distant cancer spread to places such as the lungs, liver, bones, bone marrow, CSF or to distant muscles or lymph nodes.
Risk groups
Using the information about the TNM stage, the clinical group, and the PAX/FOXO1 fusion gene status, doctors divide patients into 3 main risk groups. This helps doctors decide what treatment plan is best.
The risk groups are based on what has been learned from research of people previously treated for RMS. These risk groups are used for people under the age of 21. 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.
About 1 in 3 children with RMS fall 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/FOXO1 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/FOXO1 fusion gene
Children with TNM stage 1 RMS that fall into group I and do not have PAX/FOXO1 fusion genes have done very well with treatment in previous trials. This subgroup of children will be called the very low-risk group in the newest low-risk RMS clinical trial. This trial will treat these children with less chemo, with a goal of maintaining excellent outcomes.
About half of children with 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/FOXO1 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/FOXO1 fusion gene
- Children younger than 10 years of age with widespread (stage 4) RMS, in which the cancer cells do not have a PAX/FOXO1 fusion gene
About 1 in 5 children with RMS fall into the 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/FOXO1 fusion gene
- Children with widespread (stage 4) RMS, in which the cancer cells do have a PAX/FOXO1 fusion gene
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- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
Haduong JH, Heske CM, Allen-Rhoades W, et al. An update on rhabdomyosarcoma risk stratification and the rationale for current and future Children's Oncology Group clinical trials. Pediatr Blood Cancer. 2022;69(4):e29511.
Linardic CM, Wexler, LH. Chapter 25: Rhabdomyosarcoma. In: Blaney SM, Adamson PC, Helman LJ, eds. Pizzo and Poplack’s Principles and Practice of Pediatric Oncology. 8th ed. Philadelphia Pa: Lippincott Williams & Wilkins; 2021.
National Cancer Institute. Childhood Rhabdomyosarcoma Treatment (PDQ®). 2024. Accessed at www.cancer.gov/types/soft-tissue-sarcoma/hp/rhabdomyosarcoma-treatment-pdq on April 3, 2025.
Last Revised: June 2, 2025
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