Staging is a way of describing where the cancer is located, if or where it has spread, and whether it is affecting the functions of other organs in the body. Doctors use diagnostic tests to determine the tumor's stage, so staging may not be complete until all of the tests are finished. Knowing the stage helps the doctor to decide what kind of treatment is best and can help predict a patient's prognosis (chance of recovery). There are different stage descriptions for different tumors.

The terms doctors use to describe the stage of osteosarcoma and plan treatment include:

Localized: The tumor is only in the bone where it began and in the tissue around it. The tumor has not spread to other parts of the body.

Metastatic: The tumor has spread from the bone where it began to another part of the body, most often the lungs or other bones.

Recurrent: Recurrent osteosarcoma is a tumor that comes back either during or after treatment. It can come back in the same place where it started or in another part of the body. Osteosarcoma recurs most often in the lungs and other bones. If there is a recurrence, the cancer may need to be staged again (called re-staging) using the system above.

Source: National Cancer Institute