Staging of osteosarcoma
Staging is the process the doctor uses to find out how far the cancer has spread. The stage of the cancer 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.
Localized or metastatic
Doctors divide osteosarcomas into 2 groups when deciding on the best course of treatment – localized or metastatic.
A localized osteosarcoma affects only the bone it started in and maybe the tissues 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 tumor than can be seen is able to be removed by surgery. Osteosarcomas that cannot be fully removed by surgery are called non-resectable (or unresectable).
A metastatic osteosarcoma has clearly spread to other parts of the body not directly connected to the bone the tumor started in. 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 have a worse outlook, 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, if the tumor has grown outside of the bone, and whether 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), divides osteosarcoma into 4 stages using Roman numerals I to IV (1 to 4). Again, the higher the number, the more advanced the cancer.
Ask your doctor to explain the stage of your (or your child’s) cancer to you in terms you can understand.
Last Medical Review: 01/24/2013
Last Revised: 01/24/2013