Osteosarcoma

Other Names: Osteogenic sarcoma

Pathophysiology

• Osteosarcoma is the most common type of bone cancer.
• The average age at diagnosis is 15.
• Boys and girls have a similar incidence of this tumor until late adolescence, at which time boys are more commonly affected.
• In rare cases, osteosarcoma occurs in adults.
• Although osteosarcoma tends to occur in the larger bones, such as the shin (near the knee), thigh (near the knee) and upper arm (near the shoulder), it can occur in any bone.

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Types

A number of variants of osteosarcoma exist, including conventional types (osteoblastic, chondroblastic, and fibroblastic), telangiectatic, multifocal, parosteal, and periosteal.

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Predilections of osteosarcoma

Cause

The cause is not known. In some cases, osteosarcoma runs in families. At least one gene has been linked to an increased risk. This gene is also associated with familial retinoblastoma. This is a cancer of the eye that occurs in children.

Mechanism

Osteosarcomas tend to occur at the sites of bone growth, presumably because proliferation makes osteoblastic cells in this region prone to acquire mutations that could lead to transformation of cells (the RB gene and p53 gene are commonly involved). Due to this tendency, high incidence of osteosarcoma is seen in some large dog breeds (St. Bernards and Great Danes). The tumor may be localized at the end of the long bone (commonly in the metaphysis). Most often it affects the proximal end of tibia or humerus, or distal end of femur. Osteosarcoma tends to affect regions around the knee in 60% of cases, 15% around the hip, 10% at the shoulder, and 8% in the jaw. The tumor is solid, hard, irregular ("fir-tree," "moth-eaten", or "sun-burst" appearance on X-ray examination) due to the tumor spicules of calcified bone radiating in right angles. These right angles form what is known as a Codman triangle, which is characteristic but not diagnostic of osteosarcoma. Surrounding tissues are infiltrated.

Symptoms

The first symptom is usually bone pain near a joint. This symptom may be overlooked because of other more common causes of joint pain. Other symptoms may include any of the following:

• Bone fracture (may occur after a routine movement)
• Limitation of motion
• Limping (if the tumor is in the leg)
• Pain when lifting (if the tumor is in the arm)
• Tenderness, swelling, or redness at the site of the tumor

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Abnormality of the femoral metaphysis
• Osteolysis(Breakdown of bone)

30%-79% of people have these symptoms

• Abnormality of the tibial metaphysis
• Elevated alkaline phosphatase(Greatly elevated alkaline phosphatase)
• Increased(lactate dehydrogenase level)
• Joint swelling
• Pain

1%-4% of people have these symptoms

• Fever
• Pathologic fracture(Spontaneous fracture)
• Weight loss

Diagnosis

The health care provider will perform a physical exam and ask about the medical history and symptoms. Osteosarcoma can be diagnosed by core needle biopsy or open surgical biopsy. It is preferable that the biopsy be performed by a surgeon skilled in the techniques of limb sparing (removal of the malignant bone tumor without amputation and replacement of bones or joints with allografts or prosthetic devices). In these cases, the original biopsy incision placement is crucial. Inappropriate alignment of the biopsy or inadvertent contamination of soft tissues can render subsequent limb-preserving reconstructive surgery impossible.

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Osteosarcoma

Tests that may be done include:

• Biopsy (at time of surgery for diagnosis)
• Blood tests
• Bone scan to see if the cancer has spread to other bones
• CT scan of the chest to see if the cancer has spread to the lungs
• MRI scan
• PET scan
• X-ray

Treatment

Treatment usually starts after a biopsy of the tumor is done. Before surgery to remove the tumor, chemotherapy is usually given. This can shrink the tumor and make surgery easier. It may also kill any cancer cells that have spread to other parts of the body.

Surgery is used after chemotherapy to remove any remaining tumor. In most cases, surgery can remove the tumor while saving the affected limb. This is called limb-sparing surgery. In rare cases, more involved surgery (amputation) is necessary. The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition.

• Levoleucovorin (Brand name: Fusilev™)Levoleucovorin rescue is indicated after high-dose methotrexate therapy in osteosarcoma. Levoleucovorin is also indicated to diminish the toxicity and counteract the effects of impaired methotrexate elimination and of inadvertent overdosage of folic acid
• Leucovorin (Brand name: Leucovorin calcium®)For rescue use after high dose methotrexate therapy in the treatment of osteosarcoma.

Methotrexate sodium (Brand name: Methotrexate)For the use of high dose methotrexate with leucovorin rescue in patients with non-metastatic osteosarcoma who have undergone surgical resection or amputation for the primary tumor.

Prognosis

If the tumor has not spread to the lungs (pulmonary metastasis), long-term survival rates are better. If the cancer has spread to other parts of the body, the outlook is worse. However, there is still a chance of cure with effective treatment.

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