Stages of Osteosarcoma (Bone Cancer) Staging refers to the extent of a cancer within the body, including whether the disease has spread from the original site to other parts of the body. In order to stage a disease, doctors perform exams and tests to learn more about the disease, especially to see whether the disease has spread from the original site to other parts of the body. There are three stages of osteosarcoma. Localized The cancer cells have not spread beyond the bone or nearby tissue in which the cancer began. In young patients most tumors occur around the knee. Metastatic The cancer cells have spread from the bone in which the cancer began to other parts of the body. The cancer most often spreads to the lungs. It may also spread to other bones. Recurrent Recurrent disease means that the cancer has come back (recurred) after it has been treated. It may come back in the tissues where it first started or it may come back in another part of the body.