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Osteosarcoma is a cancer of the bone. It starts in immature bone cells that normally form new bone tissue. Osteosarcoma destroys local tissue and weakens the bone. It can occur, very rarely, as a tumor of the soft tissues of the body, outside the bone itself. Most of the time, osteosarcoma begins in the hip or shin bones. The second most common place for osteosarcoma to begin is in the upper arm bone, close to the shoulder. However, osteosarcoma can develop in any bone in the body.

Symptoms of osteosarcoma can vary, depending on the bone in which the cancer develops. Symptoms may include:

• Pain in the bone or joint that gets worse over time
• A painless swelling or a noticeable mass in the arm or leg
• A broken bone that occurs without injury or with minimal injury or trauma
• Stiffness or swelling of joints (uncommon)
• Back pain or loss of bowel or bladder control related to a tumor in the pelvis or at the base of the spine. This is very rarely the first sign that a child has osteosarcoma.

Diagnosing Osteosarcoma

Many procedures and tests may be performed to see if and where cancer cells are present. If a bone tumor is suspected, it is important that the child is diagnosed and treated by a team experienced in working with children with cancer.

Quite often, your child’s primary doctor will have completed some type of x-ray. These exams are often repeated by the specialist who will be looking for specific details of the lump or swelling. Following an x-ray, a number of other tests may be performed such as:

• CT scan of bone and chest
• MRI
• Bone Scan

The information gained from these tests will help doctors better define the location and size of the cancer, and identify whether it is interfering with other structures in the body. These are helpful pieces of information in making decisions about how to treat the cancer.

In addition to scans, a  biopsy will also be performed. During the biopsy, a piece of the tumor is removed and is examined under a microscope by a pathologist to identify the types of cells present. It is imperative that the biopsy be performed by an experienced surgeon with knowledge of sarcomas to assure that the appropriate biologic tests are done on the sample and that the biopsy does not interfere with future surgical planning.

Osteosarcomas are described by their location: central tumors arise inside the bone while surface tumors arise on the outer surface of the bone. Each type has a number of subtypes. Conventional central osteosarcomas account for the vast majority of osteosarcomas in children and adolescents.

Before treating a tumor, doctors need to know exactly how much of the cancer is present in the body both at the site of the tumor and elsewhere in the body. To evaluate this, a variety of tests may be performed, including scans of other parts of the body, such as the lungs, to see if the tumor has spread.

Doctors use the following terms to describe osteosarcoma and develop treatment plans.

• Localized: The tumor is limited to the bone of origin and the tissue surrounding the tumor; it has not spread to other parts of the body.
• Metastatic: The tumor has spread from where it began to other parts of the body. The most common sites of spread are the lungs or other bones.
• Recurrent: The tumor has come back after treatment. It can recur in the same place that it started, or in another part of the body. The lungs and other bones are the most common sites of recurrent tumors.
• Initial response to therapy: An important prognostic (predictive of treatment success) factor is the patient's response to initial therapy. Patients whose tumor cells have nearly all been eliminated after the initial 10 weeks of chemotherapy have a better outlook than those whose tumor cells do not respond as well to treatment. Investigators are working on finding biological differences that distinguish responsive from unresponsive tumors. If this can be determined at the time of diagnosis, treatment could be targeted better to the tumor and potentially improve the outlook for patients with less responsive tumor types.

Causes of Osteosarcoma

Osteosarcoma is probably caused by a combination of genetic changes that together cause immature bone cells to become cancer cells instead of developing into bone. The same gene that is commonly abnormal in patients that develop eye tumors called retinoblastoma (the RB gene) may also be associated with osteosarcoma. The RB gene is a "tumor suppressor" gene that normally controls the growth of cells. When it becomes changed, or mutated, it can no longer control cell growth and tumors can form. Defects in another tumor suppressor gene, P53, can also predispose individuals to osteosarcoma or other cancers. These gene disturbances are very rare.

Despite this information, only a few risk factors for osteosarcoma are known for sure.

Ionizing radiation (x-rays)

There is an increased risk following radiation treatment for a previous cancer. Children who receive x-rays to diagnose a medical condition, such as a broken bone or tooth decay, are NOT at increased risk.

Genetic syndromes

Children with some genetic syndromes are more likely to develop osteosarcoma than other children. The syndromes are hereditary retinoblastoma, Li-Fraumeni syndrome and Rothmund-Thomson syndrome. Children with these genetic conditions are more at risk for osteosarcoma, but these account for only a small fraction of cases. These syndromes usually require medical care, so you would know if your child had one of them.

According to the current state of medical knowledge, the following things most likely DO NOT increase a child’s risk of osteosarcoma:

• Fluoride in drinking water
• Injury to the bone

Further, researchers know that most osteosarcomas develop in people who have no other diseases and no family history of bone cancer. Osteosarcoma may be triggered by an over activity of bone cells. In a very small number of families, siblings of children with osteosarcoma can develop osteosarcoma. These families may be studied to see if a rare genetic defect may be causing the tumor. If such a defect is found, it may help doctors identify other family members that may be at risk and understand the process by which cancer develops in other patients with osteosarcoma.

Last updated July, 2011

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