Staging of osteosarcoma
The stage of a cancer is a standard summary of how far it has spread. The stage is based on the results of physical exams, imaging tests, and any biopsies that have been done, which were described in the section “How is osteosarcoma found?” The treatment and outlook for survival depend mostly on the stage of the cancer.
Osteosarcoma can be staged in different ways.
Localized or metastatic
Doctors divide osteosarcomas into 2 groups when deciding on the best course of treatment – localized or metastatic.
Localized: These osteosarcomas affect only the bone they started in and maybe the structures next to the bone, such as muscles and tendons. But even when tests do not show that the cancer has spread to distant places, most patients are likely to have very small areas of cancer spread that can’t be found with tests. This is why chemotherapy (chemo) is an important part of treatment for most patients.
Doctors further divide these osteosarcomas into 2 groups:
- Resectable cancers are those in which all of the visible tumor can be removed by surgery.
- Non-resectable (or unresectable) osteosarcomas cannot be fully removed by surgery.
Metastatic: These osteosarcomas have clearly spread to other parts of the body. Most often the spread is to the lungs, but it can also spread to other bones, the brain, or other organs.
Patients with metastases (“mets”) at the time the cancer is found are harder to treat, although some can be cured if the mets can be removed by surgery. The cure rate for these patients is much better if chemo is also given.
Musculoskeletal Tumor Society (MSTS) staging system
This system is a more detailed way to stage osteosarcoma. It is also known as the Enneking system. It takes into account:
- The grade of the tumor (based on how abnormal the cancer cells look under the microscope)
- If the main tumor has grown outside of the bone
- If the cancer has spread to nearby lymph nodes or other organs. The grade is found by looking at the cancer cells under a microscope and is used to predict how likely the cancer is to grow and spread.
These factors are combined to give an overall stage, expressed in Roman numerals from I to III (1 to 3). Some of these stages are further divided into A or B. As a rule, the higher the number, the more serious the cancer.
AJCC staging system
Another staging system, the AJCC system (American Joint Commission on Cancer), is based on 4 key pieces of information:
- T describes the size of the main tumor and whether it is in different areas of the bone
- N describes spread to nearby lymph nodes
- M tells whether the cancer has metastasized (spread) to other organs
- G stands for the grade of the tumor
These factors are combined to give an overall stage, using Roman numerals I to IV (1 to 4). Again, the higher the number, the more advanced the cancer.
The staging of osteosarcoma can be confusing, so be sure to ask your doctor to explain the stage of your (or your child’s) cancer to you in terms you can understand.
Other things that can affect a person’s outlook
The stage of the cancer is important when trying to figure out a person’s outlook, but other factors are important, too. For instance, these factors have been linked with a better outlook:
- Being younger (child or young adult, as opposed to an older adult)
- Being female
- The tumor being found in an arm or leg bone (as opposed to the hip bones)
- The tumor(s) being removed completely
- Normal results on certain blood tests
- The tumor having a good response to chemotherapy
Last Medical Review: 06/13/2014
Last Revised: 01/27/2016