Osteosarcoma is a form of bone cancer originating from cells that create new bone tissue. It is the most prevalent type of primary bone cancer, meaning it starts in the bone itself. This cancer is most often diagnosed in teenagers and young adults during their adolescent growth spurt. It develops in the long bones of the arms and legs, where the cells in these tumors produce abnormal bone.
Symptoms and Common Locations
The most common initial sign of osteosarcoma is bone pain, often mistaken for growing pains or a sports injury. The pain may start as intermittent but worsens over time, becoming more pronounced at night or with activity. A growing tumor can also cause noticeable swelling, a lump over the bone, or warmth in the affected area.
A bone weakened by the tumor may break with little or no trauma, an event known as a pathologic fracture. This can also lead to limited movement in a nearby joint, causing a limp if the tumor is in a leg bone.
Osteosarcoma develops at the ends of long bones, where growth is most active. The most common site is the area around theknee, involving the thighbone or shinbone. Another frequent location is the upper arm bone near the shoulder. Less commonly, these tumors can appear in the pelvis, jaw, or skull.
Causes and Risk Factors
The precise cause of most osteosarcoma cases is unknown. The cancer arises from mutations in the DNA of bone-forming cells, which disrupts normal cell growth and leads to the uncontrolled proliferation of abnormal cells. These cells form a tumor that can invade and destroy healthy tissue.
Certain inherited genetic syndromes, such as Li-Fraumeni syndrome and hereditary retinoblastoma, increase a person’s risk. Individuals with these conditions have a genetic predisposition that makes them more susceptible to developing osteosarcoma.
Previous medical treatments can be a factor. Exposure to radiation therapy for a prior cancer increases the risk of osteosarcoma developing in the irradiated bone. Non-cancerous bone disorders, like Paget’s disease of bone, are also associated with a higher risk, particularly in older adults. However, most people diagnosed have no identifiable risk factors.
The Diagnostic Process
Diagnosing osteosarcoma begins with a physical examination to assess the affected area for swelling, tenderness, or lumps. If a bone tumor is suspected, the first imaging step is an X-ray. X-rays can reveal bone abnormalities with a characteristic appearance that suggests osteosarcoma.
Further imaging tests are required to understand the tumor’s scope. An MRI scan provides detailed pictures of surrounding soft tissues to define the tumor’s size and extent. A CT scan is used to check if the cancer has spread to the lungs, the most common site of metastasis, while a bone scan checks for spread to other bones.
Although imaging tests can strongly indicate osteosarcoma, a biopsy is required for a definitive diagnosis. During this procedure, a pathologist examines a small sample of tumor tissue removed either by a needle or through a surgical incision. The biopsy results confirm the presence of cancer and help determine the tumor’s subtype and grade.
Standard Treatment Approaches
Treatment for osteosarcoma involves a combination of chemotherapy and surgery. The standard approach begins with neoadjuvant chemotherapy, administered before surgery. This initial treatment aims to shrink the primary tumor for easier removal and to kill any cancer cells that may have spread.
After chemotherapy, surgery is performed to remove the tumor. The goal is to remove all cancerous tissue while preserving as much function as possible. In many cases, limb-sparing surgery is performed, where the tumor is removed and the bone is reconstructed with a metal implant or bone graft. Amputation may be necessary if the tumor is too large or involves major nerves and blood vessels.
Following surgery, a second course of adjuvant chemotherapy is given to eradicate any remaining cancer cells and reduce the risk of recurrence. While chemotherapy and surgery are the primary treatments, radiation therapy may be used if a tumor cannot be completely removed surgically.
Staging and Prognosis
Once diagnosed, osteosarcoma is staged to determine the extent of the disease, which guides treatment and helps predict the outlook. The main distinction is between localized and metastatic disease. Localized osteosarcoma is confined to the bone of origin and immediate surrounding tissues.
Metastatic osteosarcoma means the cancer has spread from the primary tumor, most commonly through the bloodstream. The lungs are the most frequent site of metastasis, but it can also spread to other bones or organs. The presence of metastasis at diagnosis is a significant factor in the prognosis.
Patients with localized osteosarcoma that is completely removed by surgery and who respond well to chemotherapy have a more favorable outlook. For these individuals, long-term survival rates have improved with modern treatment protocols. The prognosis is more challenging for patients with metastatic disease or for those whose tumors do not respond well to chemotherapy.