MD2B - Pediatric Oncology: Osteosarcoma

Overview

Osteosarcoma is the most common type of primary bone cancer to occur in children. It arises from those cells that produce new bone and is therefore characterized by the appearance of immature bone tissue. This type of cancer is seen most frequently in adolescents and young adults, suggesting an association between rapid bone growth and tumor formation. It accounts for approximately 5% of childhood tumors and approximately 400 new cases of osteosarcoma are diagnosed in children less than twenty years of age each year in the United States. Boys are affected more frequently than girls, and African Americans are affected more frequently than Caucasians. Although osteosarcoma can occur in any bone, it is most frequently seen in large bones with rapid bone growth rates such as the distal femur (thigh bone), proximal tibia (shin bone), and the proximal humerus (arm bone). Osteosarcoma often spreads to the lungs and to other bones.

Symptoms

Osteosarcoma most frequently presents with pain, swelling, redness, or limitation of movement at the site of the tumor. When the tumor is located in the leg, children may develop a limp. When the tumor is located in the arm, children may develop arm weakness and may be unable to lift heavy objects. Sometimes, the cancer can weaken the bone and the child may sustain a fracture with only minimal trauma. As these tumors occur most frequently in active adolescents, complaints are often initially misdiagnosed as being the result of a sports injury. Any bone or joint pain that does not respond to conservative therapies such as rest and icing should be investigated more thoroughly to rule out serious causes of bone pain such as infection or cancer.

Diagnosis

A physician will perform a physical examination, schedule imaging tests, and order laboratory tests to help distinguish osteosarcoma from other bone disorders.

Imaging studies

• x-rays: a diagnostic test using energy beams to produce images of internal tissues, bones, and organs. In osteosarcoma a s clerotic lesion is observed that is often described as a "sunburst pattern."Commonly, elevation of the periosteum may appear and give the characteristic "Codman's triangle".
• bone scans: a diagnostic test using nuclear imaging to appreciate bone degeneration, inflammation, or tumor.
• magnetic resonance imaging (MRI): a diagnostic test using large magnets and radiofrequency signals connected to a computer to produce detailed images of structures within the body including the spinal cord and nerve fibers.
• CT or CAT scan: a diagnostic imaging test that uses x-rays and computer technology to produce cross-sectional images of slices of the body. If osteosarcoma is suspected, a chest CT will also be performed to make sure that the cancer has not spread to the lungs.

Tissue samples

Samples from the primary tumor and from the bone marrow will be removed by inserting a needle into the tumor and into the hip bones. These samples will be examined under the microscope to look for cells that are abnormal or cancerous. Obtaining an actual tissue sample through biopsy is important to distinguish osteosarcoma from other bone problems including Ewing's sarcoma and osteomyelitis.

Treatment

Prior to the use of chemotherapy (which began in the 1970s), osteosarcoma was treated only with surgical resection, usually in the form of a limb amputation. In more than 80% of patients, metastatic disease would quickly develop, often in the lungs. The addition of chemotherapy to treatment protocols has greatly increased survival rates for osteosarcoma. Unlike Ewing's sarcoma, osteosarcoma is not very responsive to radiation therapy.

Surgery

Surgery is used to gain local control over the cancer. Surgery can take the form of total limb amputation where the whole arm or leg is removed, or a limb-salvage procedure where only the tumor and some surrounding healthy tissue are taken. If a limb salvage procedure is done, the removed bone or joint can be replaced with allografts or prosthetic devices. The choice between limb amputation and limb salvage surgery depends on tumor characteristics such as location, size, and spread, as well as patient characteristics including age, bone development, and lifestyle choices. In patients with osteosarcoma that has not spread beyond the bone, researchers have found no difference in overall survival between limb-sparing surgery and total amputation.

Chemotherapy

Chemotherapy is a systemic treatment and travels throughout the body. Chemo can be used before surgery to shrink the tumor. It can also be utilized after surgery to get rid of any cells that may have escaped from the primary site.

Prognosis

The addition of chemotherapy to treatment regimens has greatly increased survival rates of children with osteosarcoma. Over 70% of patients who present with localized disease achieve long term survival. Patients who have pelvic tumors do less well, and patients who have metastases at the time of diagnosis have survival rates under 30%.

Osteosarcoma Risks

Certain genetic conditions and environmental factors have been associated with the development of osteosarcoma. Retinoblastoma, Li-Fraumeni syndrome, Rothmund-Thomson syndrome, Ollier's disease, osteogenesis imperfecta, polyostotic fibrous dysplasia and Paget's disease have all been observed to increase the likelihood of developing osteosarcoma. In addition, high dose radiation has been found to increase one's risk of developing osteosarcoma. Some children who have received irradiation as part of their treatment for another cancer go on to develop osteosarcoma as a secondary cancer.