Osteosarcoma, Part 1 — Introduction, Incidence, Symptoms and Treatment

What is osteosarcoma?

Osteosarcoma (AH'-stee-oh-sar-koh'-muh), aka osteogenic sarcoma, is a cancer that makes abnormal bone. It usually starts within bone, and rarely begins in muscle. Osteosarcoma is the most common type of sarcoma (cancer of bone and soft tissues) in adolescents. However, it is occasionally diagnosed in younger children and older adults. The incidence of osteosarcoma seems to peak at the same time that adolescents are growing most rapidly. Due to this association, research has sought a correlation between osteosarcoma and the levels of growth hormone. To date, no clear link between the two has been found. In addition, there is no indication that osteosarcoma is more common among children who are taller or who grow more rapidly. Osteosarcoma is also seen more frequently in the metaphyses (meh-TAH'-fih-seez). These locations are very active during rapid bone growth, and lie next to the physes (FEYE'-seez) or growth plates. These growth plates are located near the ends of long bones (near the joints) and are also found in the pelvis. Osteosarcoma rarely occurs in the spine.

Incidence and prevalence

The annual incidence of osteosarcoma in the U.S., among people younger than 20, is 5.2 cases per million for blacks, and 4.6 cases per million for whites. Among males, the incidence is 5.2 cases per million, and among females it is 4.5 cases per million. When the annual incidence is stratified by age in more detail, the data show:

Age Blacks Whites
All under 20 5.2 4.6
Under 5 less than 0.5
5-9 2.6 2.1
10-14 8.3 7.0
15-19 8.9 8.2

This table shows the changes in incidence of this disease during development. Osteosarcoma is very rare in young children below 5 (approximately 0.5 cases per million). Annual incidence increases steadily with age, reaching a dramatic increase during the adolescent growth spurt. For children between the ages of 5 and 9, the incidence is 2.6 cases per million for blacks and 2.1 cases per million for whites. In children between the ages of 10 and 14, the incidence is 8.3 cases per million for blacks and 7 cases per million for whites. The racial disparity at this age could be a result of the earlier onset of puberty among black girls and therefore an earlier growth spurt. Among those between 15 and 19 years, the incidence is 8.9 cases per million for blacks and 8.2 cases per million for whites.

Symptoms

Osteosarcoma often starts near the joints.

Children with osteosarcoma usually go to their doctor because of pain. The pain sometimes involves the adjacent joint. Occasionally, a mass or lump can be felt, which may not hurt. Because injuries due to sports and other activities are much more common that osteosarcoma, the doctor may at first blame the child's pain on an injury. Later, when the pain does not improve, the doctor may run other tests, which result in the diagnosis of osteosarcoma. Specific clues, which may suggest that the pain is not due to an injury and therefore requires further tests, include:  no specific history of an injury; a mass felt in the area of the pain; pain that exceeds the degree of the assumed injury; pain that continues longer than expected; and pain occurring even when the child is resting, such as during the night. It is unusual for children to have pain that continues for more than several days. Any child or adolescent who has long-standing pain needs to see the doctor.

The diagnosis of osteosarcoma may be suspected following regular X-rays. However, when an X-ray film shows a change that suggests osteosarcoma, the doctor will often look at another type of test called a magnetic resonance imaging (MRI) scan. The diagnosis requires a biopsy, in which a sample of tissue is removed from the mass and examined under a microscope to determine the type of cancer present. As stated previously, osteosarcoma often will metastasize, or spread though the blood stream, to the lungs and other bones. Therefore, the doctor will check the lungs with a computed tomography scan (CAT or CT scan) and examine the entire skeleton using a "bone scan".

Treatment

Decades ago, treatment for osteosarcoma was limited to a surgical procedure to remove the tumor. Because metastases, or spread of the tumor, frequently developed prior to diagnosis, survival was extremely poor. During the 1970s, the development of effective chemotherapy drugs led to a dramatic improvement in survival from this cancer. Radiation therapy is not used for osteosarcoma, because this cancer does not respond to radiation.

Osteosarcoma extending into surrounding tissue.

Treatment of the original tumor consists of a surgical procedure to remove the tumor and the involved bone, referred to as "excision". Although osteosarcoma does not begin in soft tissues, the tumor will often extend from the bone into the soft tissue. During the removal of the tumor, some soft tissue may be lost due to the the need to remove the entire cancer. If the function of the limb is compromised by the removal of all the affected tissues, amputation of part or all of the limb might be necessary. If the limb can be saved while removing the tumor completely, the bone is replaced; either with a large piece of metal designed to look like the removed bone (similar to the joint replacements done in older adults with arthritis) or with a piece of stored, frozen bone that is the same size and shape as the removed bone.

This type of surgery is called "limb salvage" surgery. Sometimes, the affected arm or leg may not grow the same as the other side, particularly if the growth plates (the site of bone growth) were destroyed by the cancer. Following limb salvage surgery, the reconstructed bone will not be as strong as the original bone, resulting in an increased risk of breaking or failure over the child's lifetime. Activities must be restricted during the initial healing period. The extent and duration of these restrictions depend on the exact nature of the reconstruction, and is determined individually for each child. For example, if a reconstruction requires bones to heal, the child might need to avoid vigorous activities for several months.

International studies continue to search for the best combination of medications, one that will efficiently kill the tumor cells but will cause few side effects. Different kinds of anti-cancer medications, or chemotherapy, are used to treat osteosarcoma. A chemotherapy regimen typically lasts about a year, and comprises 12 courses of chemotherapy. A "course" often consists of a few days of medication, followed by about three weeks of rest. Typically, the child will first receive about 10 weeks of chemotherapy before the tumor is removed surgically. This allows the doctor to evaluate how well the tumor responds to the chemotherapy. Obviously, the more cancer cells that die during the chemotherapy, the greater the likelihood that the child will enjoy long-term survival. After healing from the surgery, the child is placed back on chemotherapy until the rest of the courses of medicine are completed.

Most chemotherapy for osteosarcoma is given through the child's vein, as an intravenous or "IV" medication. Providing chemotherapy in this manner allows the medication to get into the body more rapidly than if it were given by another route, and permits the use of stronger drugs. Many children have a semi-permanent intravenous catheter implanted during surgery. This device allows chemotherapy to go into a large vein. With this device, children will not have the discomfort of a needle insertion each time they receive chemotherapy.


For more information

Part 2 — Possible Side Effects, Restrictions, and Implications for School

Curesearch
http://www.curesearch.org/

National Library of Medicine/National Institutes of Health
http://www.nlm.nih.gov/medlineplus/ency/article/001302.htm

Contributed by:

Kim Templeton, MD
Professor
Department of Orthopedic Surgery
University of Kansas Medical Center

Kathy Davis, MSEd, PhD
Associate Professor
Project Director, Connected Kansas Kids
Director, KU Kids Healing Place
University of Kansas Medical Center