The second large group of sarcoma is bone sarcomas or bone cancer. There are three types of bone sarcoma: osteosarcoma; Ewing’s sarcoma; and chondrosarcoma. Bone sarcomas very rare with approximately 2,890 new cases diagnosed in the United States each year, and approximately 1,410 deaths. The incidence is slightly higher in males than females and no race has a higher incidence than another, although, Ewing’s sarcoma is more among Americans of European descent. Bone sarcomas are very likely to be diagnosed in children; and due to the rarity and severity of bone cancer, a bone cancer specialist such as a pediatric oncologist or an orthopedic oncologist should be consulted in the treatment of the disease.
Bones consist of three types of tissue: compact tissue (the hard outer portion of the bone), cancellous tissue (spongy tissue inside the bone containing the bone marrow), and subchondral tissue (the smooth bone tissue of the joints). Cartilage surrounds the subchondral tissue to form a cushion around the joints.
Bone tumors can be benign (non-cancerous) or malignant (cancerous). Benign bone tumors are rarely life threatening and do not spread within the body; however, they can grow and compress healthy bone tissue. Cancer that develops in the bone is called primary bone cancer. It is differentiated by secondary bone cancer which spreads to the bone from another part of the body. Primary bone cancer is rare with approximately 2,500 new cases diagnosed each year in the United States (this figure includes bone cancer which is not sarcoma).
The most common type of primary bone cancer is osteosarcoma. Because it occurs in growing bones, it is most often found in children. Another type of primary bone cancer is chondrosarcoma which is found in the cartilage. This cancer occurs more often in adults. Ewing’s sarcoma can occur as either a bone sarcoma or a soft tissue sarcoma depending upon the original location in the tumor.
Scientists are uncertain what causes bone cancer however they have been able to identify some factors which may put a person at risk. Children and young adults who have had undergone radiation therapy or chemotherapy for other diseases are at increased risk for bone cancer. Additionally, adults with Paget’s disease which is a disease characterized by abnormal growth of new bone cells have an increased risk of osteosarcoma. There are also some hereditary conditions which can increase the risk of bone cancer.
Symptoms of bone cancer can vary depending on the size and location of the tumor. Pain is the most common symptom. Tumors arising in or around the joints often cause swelling and tenderness. Tumors can also weaken the bones thus causing fractures. Some other symptoms can be weight loss, fatigue and or anemia.
The first step in diagnosing primary bone cancer is a complete medical history and physical examination performed by a physician. The doctor may order a blood test to determine the level of an enzyme called alkaline phosphatase. Approximately 55% of patients with primary bone cancer will have elevated levels of alkaline phosphatase. However, it isn’t a completely reliable indicator for bone cancer since growing bones in children will cause the enzyme to be elevated.
X-rays are also used to locate a tumor. If an x-ray suggests a tumor is present than a doctor may require further testing such as a CT scan, Magnetic Resonance Imaging (MRI), or an angiogram. Finally, a biopsy must be performed to determine if cancer is present. A biopsy is a procedure used to remove sample tissue from the tumor. A surgeon, usually an orthopedic oncologist, performs the procedure using a needle or making an incision. During a needle biopsy the surgeon makes a small hole in the bone and removes sample tissue with a small instrument. During an incisional biopsy, the surgeon cuts into the tumor and removes sample tissue. A Pathologist (a doctor specializing in identifying disease) then studies the cells and tissues under a microscope to determine whether the tumor is cancerous.
The treatment of bone cancer depends on the size, location, type and stage of the cancer. Chemotherapy with surgery is often the primary treatment. While amputation of a limb is sometimes necessary, using chemotherapy either before or after surgery has allowed physicians to save the limb and improve survival in many cases. Radiation may be used in Ewing’s sarcoma is surgery is not feasible or in certain select cases of metastatic disease.
New and more effective treatments are being developed in clinical trials at many hospitals and cancer centers in the United States.
See also our list of specific sub-types of bone sarcomas.