Once the type of rhabdomyosarcoma (RMS) has been identified, doctors need to assess, as accurately as possible, how much of it there is and where it has spread. The answers to "how much" and "where" are expressed in a 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 try to determine 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.
Staging for RMS is fairly complex. 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 along with the child's age to divide patients into risk groups, which then are used to determine the best treatment options.
The TNM stage
The TNM stage is based on 3 key pieces of information prior to treatment:
- T: The characteristics of the tumor (location and size)
- N: Whether the cancer has spread to nearby lymph nodes
- 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 near the eye)
- The head and neck area, except for parameningeal sites (next to the membranes covering the brain)
- A genital or urinary site, except the bladder or prostate
- 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 sites.
Stage 2
The tumor started in an unfavorable site:
- The bladder or prostate
- An arm or leg
- A parameningeal site (next to the membranes covering the brain)
- Any other site 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 sites.
Stage 3
The tumor started in an unfavorable site:
- The bladder or prostate
- An arm or leg
- A parameningeal site (next to the membranes covering the brain)
- Any other site 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 sites.
Stage 4
The tumor can have started at any site and can be of any size. It has spread to distant sites 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 completely removed by surgery. Group I has 2 subgroups:
Group IA: Children in this group had a tumor that was still confined to the muscle or organ where it started and was completely removed by surgery. It had not spread to nearby lymph nodes or distant sites.
Group IB: Children in this group had a tumor that had grown beyond the muscle or organ where it started and into nearby structures, but it was completely removed by surgery. It had not spread to nearby lymph nodes or distant sites.
About 15% of RMS patients are in group I.
Group II
This group includes children who have had tumors that have been removed by surgery, but cancer has been found around the edges of the removed specimen, in the nearby lymph nodes, or in both places. In all cases, as much of the cancer has been removed as possible. Group II has 3 subgroups:
Group IIA: In this group, the cancer has not spread to nearby lymph nodes or elsewhere. The surgeon has removed all the cancer that could be seen, but the pathologist has found cancer at the edge of the removed specimen, which means that there may have been a small amount of cancer left behind.
Group IIB: In this group, the cancer has spread to nearby lymph nodes, but all of the cancer has been removed by surgery.
Group IIC: In this group, the cancer has spread to nearby lymph nodes. The surgeon has removed all the cancer that could be seen (including in the lymph nodes), but the pathologist has found cancer at the edge of the removed specimen, which means that there may have been a small amount of cancer left behind.
About 20% of RMS patients are in group II.
Group III
These children have tumors that cannot be completely removed, leaving some tumor behind that can be seen with the naked eye. The tumor may have spread to nearby lymph nodes, but there is no sign that it has spread to distant organs. Group III has 2 subgroups:
Group IIIA: The tumor cannot be completely removed by surgery, and only a biopsy of the tumor has been done.
Group IIIB: The tumor cannot be completely removed, but surgery has removed at least half of the tumor.
About 50% of patients with RMS are in group III.
Group IV
These children have evidence of distant spread at the time of diagnosis to places such as the lungs, liver, bones, bone marrow, or to distant muscles or lymph nodes.
About 15% of children with RMS 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 defined based on what has been learned from previous research on patients' outcomes. The risk 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
This group 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
This group 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 sites (stage 1, 2, or 3)
High-risk group
This group includes:
- Children with widespread (stage 4) RMS (ERMS or ARMS)
Feedback
