Osteosarcoma

OBJECTIVES

The learner will be better able to:
1) Explain the principles reflected in the history and discovery of osteosarcoma
2) Generate a differential diagnosis given a patient case
3) Describe the distinct features of a radiological image of a patient with osteosarcoma
4) Explain factors that influence the incidence of osteosarcoma in a given population
5) Identify classic features of osteosarcoma given a patient case

INTRODUCTION

Osteosarcoma is a rare bone tumor that develops during periods of rapid growth in adolescents and young adults. Osteosarcoma is classified as a primary bone cancer because it begins in bone and may spread to other parts of the body. Cancer that originates in other tissues but spreads via blood circulation to bone is classified as secondary bone cancer or metastatic bone cancer.

Osteosarcoma frequently begins in long bones that are undergoing the fastest growth, usually the femur, humerus and tibia. The spread of cells via the circulatory or lymphatic system to healthy organs, such as the lungs, is called metastasis.

EPIDEMIOLOGY

According to the National Cancer Institute, primary bone cancers are diagnosed at the rate of 2,500 new cases per year in the United States. Among the primary bone cancers, osteosarcoma is the most common. The disease is most often observed in adolescents and young adults between the ages of 15 and 30.

The World Health Organization has two basic classifications with several subtypes within each group. The central (medullary) group includes the following subtypes: conventional central, telangiectactic, intraosseous well-differentiated and small cell osteosarcoma. The surface (peripheral) group includes the following subtypes: parosteal well-differentiated, periosteal and high-grade surface osteosarcoma.

ETIOLOGY

Osteosarcoma is the formation of malignant osteoid tissue. According to one clinical trial, the Multi-Institutional Osteosarcoma Study, more than half of the patients developed metastases within six months of diagnosis. Another clinical trial revealed that 85 to 95% of metastatic disease is in the lungs.

CLINICAL DIAGNOSIS AND MANIFESTATIONS

Pain is the most common symptom reported by patients with osteosarcoma. The symptoms may vary depending on the duration and location of the cancer. Patients who develop osteosarcoma in the long bones of the thigh or leg will often experience pain and stiffness in the knee joint. The degree of pain can vary between patients and is often determined by the proximity to surrounding nerves or skeletal structures. Patients commonly experience fatigue, fever and weight loss. Bones may weaken and fracture easily. A fracture at the site of the tumor is termed a pathologic fracture and has its own treatment implications.

DIFFERENTIAL DIAGNOSIS

Osteosarcomas are one of several bone tumors based on the tissue: Ewing’s sarcoma (connective tissue surrounding bone), chondrosarcoma (cartilage) and fibrosarcoma (bone, nerves, surrounding tissues). Ewing's sarcoma affects patients belonging to a similar age group. Diagnosis requires further histologic examination. Other conditions that affect bone may mimic osteosarcoma are osteomyelitis and Paget Disease of Bone.
A thorough medical examination, consisting of radiographs, bone scan, magnetic resonance imaging (MRI) and biopsy (tissue sample) can provide further insight and confirm the diagnosis of osteosarcoma.

TREATMENT

There are three types of therapy commonly used to treat osteosarcoma: chemotherapy, radiation and surgery. Surgery includes tumor removal, limb salvage or amputation, depending on the location and stage of the disease.

SUMMARY

Osteosarcoma is a primary bone cancer. It usually affects the long bones of young adults between the age of 15 and 30, although it is not limited to this age group. The signs and symptoms include bone pain, tenderness, swelling and discomfort. The extent to which the cancer has spread can determine the location and degree of pain. If the cancer becomes metastatic, it can spread to other tissues and cause further symptoms.

REFERENCES

1. Bacci G, Briccoli A, Mercuri M, et al.: Osteosarcoma of the extremities with synchronous lung metastases: long-term results in 44 patients treated with neoadjuvant chemotherapy. J Chemother 10 (1): 69-76, 1998.

2. Schajowicz F, Sissons HA, Sobin LH: The World Health Organization's histologic classification of bone tumors. A commentary on the second edition. Cancer 75 (5): 1208-14, 1995.

3. Okada K, Unni KK, Swee RG, et al.: High grade surface osteosarcoma: a clinicopathologic study of 46 cases. Cancer 85 (5): 1044-54, 1999.

4. Link MP, Goorin AM, Horowitz M, et al.: Adjuvant chemotherapy of high-grade osteosarcoma of the extremity. Updated results of the Multi-Institutional Osteosarcoma Study. Clin Orthop (270): 8-14, 1991.

5. Harris MB, Gieser P, Goorin AM, et al.: Treatment of metastatic osteosarcoma at diagnosis: a Pediatric Oncology Group Study. J Clin Oncol 16 (11): 3641-8, 1998.

6. Scully SP, Ghert MA, Zurakowski D, et al.: Pathologic fracture in osteosarcoma : prognostic importance and treatment implications. J Bone Joint Surg Am 84-A (1): 49-57, 2002.