Several different kinds of tumors can grow in bones: primary bone tumors, which form from bone tissue and can be malignant (cancerous) or benign (not cancerous), and metastatic tumors (tumors that develop from cancer cells that formed elsewhere in the body and then spread to the bone). Malignant primary bone tumors (primary bone cancers) are less common than benign primary bone tumors. Both types of primary bone tumors may grow and compress healthy bone tissue, but benign tumors usually do not spread or destroy bone tissue and are rarely a threat to life.
Primary bone cancers are included in the broader category of cancers called sarcomas. (Soft-tissue sarcomas—sarcomas that begin in muscle, fat, fibrous tissue, blood vessels, or other supporting tissue of the body, including synovial sarcoma—are not addressed in this article.)
Primary bone cancer is rare. It accounts for much less than 1% of all new cancers diagnosed. In 2018, an estimated 3,450 new cases of primary bone cancer will be diagnosed in the United States.
Cancer that metastasizes (spreads) to the bones from other parts of the body is called metastatic (or secondary) bone cancer and is referred to by the organ or tissue in which it began—for example, as breast cancer that has metastasized to the bone. In adults, cancerous tumors that have metastasized to the bone are much more common than primary bone cancer. For example, at the end of 2008, an estimated 280,000 adults ages 18–64 years in the United States were living with metastatic cancer in bones.
Although most types of cancer can spread to the bone, bone metastasis is particularly likely with certain cancers, including breast and prostate cancers. Metastatic tumors in the bone can cause fractures, pain, and abnormally high levels of calcium in the blood, a condition called hypercalcemia.
What are the different types of primary bone cancer?
Types of primary bone cancer are defined by which cells in the bone give rise to them.
Osteosarcoma arises from bone-forming cells called osteoblasts in osteoid tissue (immature bone tissue). This tumor typically occurs in the arm near the shoulder and in the leg near the knee in children, adolescents, and young adults but can occur in any bone, especially in older adults. It often grows quickly and spreads to other parts of the body, including the lungs. Risk of osteosarcoma is highest among children and adolescents ages 10 and 19. Males are more likely than females to develop osteosarcoma.
Among children, osteosarcoma is more common in blacks and other racial/ethnic groups than in whites, but among adults it is more common in whites than in other racial/ethnic groups. People who have Paget disease (a benign bone condition characterized by abnormal development of new bone cells) or a history of radiation to their bones also have an increased risk of developing osteosarcoma
Chondrosarcoma begins in cartilaginous tissue. Cartilage is a type of connective tissue that covers the ends of bones and lines the joints. Chondrosarcoma most often forms in the pelvis, upper leg, and shoulder and usually grows slowly, although sometimes it can grow quickly and spread to other parts of the body. Chondrosarcoma occurs mainly in older adults (over age 40). The risk increases with advancing age. A rare type of chondrosarcoma called extraskeletal chondrosarcoma does not form in bone cartilage. Instead, it forms in the soft tissues of the upper part of the arms and legs
Ewing sarcoma usually arises in bone but may also rarely arise in soft tissue (muscle, fat, fibrous tissue, blood vessels, or other supporting tissue). Ewing sarcomas typically form in the pelvis, legs, or ribs, but can form in any bone. This tumor often grows quickly and spreads to other parts of the body, including the lungs. The risk of Ewing sarcoma is highest in children and adolescents younger than 19 years of age. Boys are more likely to develop Ewing sarcoma than girls. Ewing sarcoma is much more common in whites than in blacks or Asians
Chordoma is a very rare tumor that forms in bones of the spine. These tumors usually occur in older adults and typically form at the base of the spine (sacrum) and at the base of the skull. About twice as many men as women are diagnosed with chordoma. When they do occur in younger people and children, they are usually found at the base of the skull and in the cervical spine (neck)
Several types of benign bone tumors can, in rare cases, become malignant and spread to other parts of the body. These include giant cell tumor of bone (also called osteoclastoma) and osteoblastoma. Giant cell tumor of bone mostly occurs at the ends of the long bones of the arms and legs, often close to the knee joint. These tumors, which typically occur in young and middle-aged adults, can be locally aggressive, causing destruction of bone.
In rare cases they can spread (metastasize), often to the lungs. Osteoblastoma replaces normal hard bone tissue with a weaker form called osteoid. This tumor occurs mainly in the spine. It is slow-growing and occurs in young and middle-aged adults. Rare cases of this tumor becoming malignant have been reported.
What are the possible causes of bone cancer?
Although primary bone cancer does not have a clearly defined cause, researchers have identified several factors that increase the likelihood of developing these tumors.
- Previous cancer treatment with radiation, chemotherapy, or stem cell transplantation. Osteosarcoma occurs more frequently in people who have had high-dose external radiation therapy (particularly at the location in the body where the radiation was given) or treatment with certain anticancer drugs, particularly alkylating agents; those treated during childhood are at particular risk. In addition, osteosarcoma develops in a small percentage (approximately 5%) of children undergoing myeloablative hematopoietic stem cell transplantation.
- Certain inherited conditions. A small number of bone cancers are due to hereditary conditions. For example, children who have had hereditary retinoblastoma (an uncommon cancer of the eye) are at a higher risk of developing osteosarcoma, particularly if they are treated with radiation. Members of families with Li-Fraumeni syndrome are at increased risk of osteosarcoma and chondrosarcoma as well as other types of cancer. Additionally, people who have hereditary defects of bones have an increased lifetime risk of developing chondrosarcoma. Childhood chordoma is linked to tuberous sclerosis complex, a genetic disorder in which benign tumors form in the kidneys, brain, eyes, heart, lungs, and skin. Although Ewing sarcoma is not strongly associated with any heredity cancer syndromes or congenital childhood diseases, accumulating evidence suggests a strong inherited genetic component to Ewing sarcoma risk.
- Certain benign bone conditions. People over age 40 who have Paget disease of bone (a benign condition characterized by abnormal development of new bone cells) are at increased risk of developing osteosarcoma
What are the symptoms of bone cancer?
Pain is the most common symptom of bone cancer, but not all bone cancers cause pain. Persistent or unusual pain or swelling in or near a bone can be caused by cancer or by other conditions. Other symptoms of bone cancer include a lump (that may feel soft and warm) in the arms, legs, chest, or pelvis; unexplained fever; and a bone that breaks for no known reason. It is important to see a doctor to determine the cause of any bone symptoms.
How is bone cancer diagnosed?
To help diagnose bone cancer, the doctor asks about the patient’s personal and family medical history. The doctor also performs a physical examination and may order laboratory and other diagnostic tests. These tests may include the following:
- X-rays, which can show the location, size, and shape of a bone tumor. If x-rays suggest that an abnormal area may be cancer, the doctor is likely to recommend special imaging tests. Even if x-rays suggest that an abnormal area is benign, the doctor may want to do further tests, especially if the patient is experiencing unusual or persistent pain.
- A bone scan, which is a test in which a small amount of radioactive material is injected into a blood vessel and travels through the bloodstream; it then collects in the bones and is detected by a scanner.
- A computed tomography (CT or CAT) scan, which is a series of detailed pictures of areas inside the body, taken from different angles, that are created by a computer linked to an x-ray machine.
- A magnetic resonance imaging (MRI) procedure, which uses a powerful magnet linked to a computer to create detailed pictures of areas inside the body without using x-rays.
- A positron emission tomography (PET) scan, in which a small amount of radioactive glucose (sugar) is injected into a vein, and a scanner is used to make detailed, computerized pictures of areas inside the body where the glucose is used. Because cancer cells often use more glucose than normal cells, the pictures can be used to find cancer cells in the body.
- An angiogram, which is an x-ray of blood vessels.
- Biopsy (removal of a tissue sample from the bone tumor) to determine whether cancer is present. The surgeon may perform a needle biopsy, an excisional biopsy, or an incisional biopsy. During a needle biopsy, the surgeon makes a small hole in the bone and removes a sample of tissue from the tumor with a needle-like instrument. For excisional biopsy, the surgeon removes an entire lump or suspicious area for diagnosis. In an incisional biopsy, the surgeon cuts into the tumor and removes a sample of tissue. Biopsies are best done by an orthopedic oncologist (a doctor experienced in the treatment of bone cancer) because the placement of the biopsy incision can influence subsequent surgical options. A pathologist (a doctor who identifies disease by studying cells and tissues under a microscope) examines the tissue to determine whether it is cancerous.
- Blood tests to determine the levels of two enzymes called alkaline phosphatase and lactate dehydrogenase. Large amounts of these enzymes may be present in the blood of people with osteosarcoma or Ewing sarcoma. High blood levels of alkaline phosphatase occur when the cells that form bone tissue are very active—when children are growing, when a broken bone is mending, or when a disease or tumor causes production of abnormal bone tissue. Because high levels of alkaline phosphatase are normal in growing children and adolescents, this test is not a reliable indicator of bone cancer.
How is primary bone cancer treated?
Treatment options depend on the type, size, location, and stage of the cancer, as well as the person’s age and general health. Treatment options for bone cancer include surgery, chemotherapy, radiation therapy, cryosurgery, and targeted therapy.
- Surgery is the usual treatment for bone cancer. The surgeon removes the entire tumor with negative margins (that is, no cancer cells are found at the edge of the tissue removed during surgery). The surgeon may also use special surgical techniques to minimize the amount of healthy tissue removed along with the tumor.
Dramatic improvements in surgical techniques and preoperative tumor treatment have made it possible for most patients with bone cancer in an arm or leg to avoid radical surgical procedures (that is, removal of the entire limb). However, most patients who undergo limb-sparing surgery need reconstructive surgery to regain limb function.
- Chemotherapy is the use of anticancer drugs to kill cancer cells. Patients who have Ewing sarcoma (newly diagnosed and recurrent) or newly diagnosed osteosarcoma usually receive a combination of anticancer drugs before undergoing surgery. Chemotherapy is not typically used to treat chondrosarcoma or chordoma.
- Radiation therapy, also called radiotherapy, involves the use of high-energy x-rays to kill cancer cells. This treatment may be used in combination with surgery. It is often used to treat Ewing sarcoma. It may also be used with other treatments for osteosarcoma, chondrosarcoma, and chordoma, particularly when a small amount of cancer remains after surgery. It may also be used for patients who are not having surgery.
A radioactive substance that collects in bone, called samarium, is an internal form of radiation therapy that can be used alone or with stem cell transplant to treat osteosarcoma that has come back after treatment in a different bone.
- Cryosurgery is the use of liquid nitrogen to freeze and kill cancer cells. This technique can sometimes be used instead of conventional surgery to destroy tumors in bone.
- Targeted therapy is the use of a drug that is designed to interact with a specific molecule involved in the growth and spread of cancer cells. The monoclonal antibody denosumab (Xgeva®) is a targeted therapy that is approved to treat adults and skeletally mature adolescents with giant cell tumor of bone that cannot be removed with surgery. It prevents the destruction of bone caused by a type of bone cell called an osteoclast.
What are the side effects of treatment for bone cancer?
People who have been treated for bone cancer have an increased likelihood of developing late effects of treatment as they age. These late effects depend on the type of treatment and the patient’s age at treatment and include physical problems involving the heart, lung, hearing, fertility, and bone; neurological problems; and second cancers (acute myeloid leukemia, myelodysplastic syndrome, and radiation-induced sarcoma).
Treatment of bone tumors with cryosurgery may lead to the destruction of nearby bone tissue and result in fractures, but these effects may not be seen for some time after the initial treatment.
Bone cancer sometimes metastasizes, particularly to the lungs, or can recur (come back), either at the same location or in other bones in the body. People who have had bone cancer should see their doctor regularly and should report any unusual symptoms right away. Follow-up varies for different types and stages of bone cancer. Generally, patients are checked frequently by their doctor and have regular blood tests and x-rays. Regular follow-up care ensures that changes in health are discussed and that problems are treated as soon as possible.