Osteosarcoma is the most common type of bone cancer, and the sixth most common type of cancer in children. Although other types of cancer can eventually spread to parts of the skeleton, osteosarcoma is one of the few that actually begin in bones and sometimes spread (or metastasize) elsewhere, usually to the lungs or other bones. Because osteosarcoma usually develops from osteoblasts (the cells that make growing bone), it most commonly affects teens who are experiencing a growth spurt. Boys are more likely to have osteosarcoma than girls, and most cases of osteosarcoma involve the knee.
Most osteosarcomas arise from random and unpredictable errors in the DNA of growing bone cells during times of intense bone growth. There currently isn't an effective way to prevent this type of cancer. But with the proper diagnosis and treatment, most kids with osteosarcoma do recover.
Risk for Childhood Osteosarcoma
Osteosarcoma is most often seen in teenage boys, and evidence shows that teens who are taller than average have an added risk for developing the disease.
Kids who have inherited one of the rare cancer syndromes also are at higher risk for osteosarcoma. These syndromes include retinoblastoma (a malignant tumor that develops in the retina, usually in children younger than age 2) and Li-Fraumeni syndrome (a kind of inherited genetic mutation). Because exposure to radiation is another trigger for DNA mutations, children who have received radiation treatments for a prior episode of cancer are also at increased risk for osteosarcoma.
Symptoms of Osteosarcoma
The most common symptoms of osteosarcoma are pain and swelling in a child's leg or arm. It occurs most often in the longer bones of the body — such as above or below the knee or in the upper arm near the shoulder. Pain may be worse during exercise or at night, and a lump or swelling may develop in the affected area up to several weeks after the pain starts. Pain that persistently wakes the child up at night or pain at rest are of particular concern. In osteosarcoma of the leg, the child may also develop an unexplained limp. In some cases, the first sign of the disease is a broken arm or leg, because the cancer has weakened the bone to make it vulnerable to a break.
If your child or teen has any of the above symptoms, it's important to see a doctor.
Diagnosing Osteosarcoma
To diagnose osteosarcoma, the doctor will likely perform a physical exam, obtain a detailed medical history, and order X-rays to detect any changes in bone structure. The doctor may also order a magnetic resolution imaging (MRI) scan of the affected area, which will find the best area to biopsy and show whether the osteosarcoma has spread from the bone into nearby muscles and fat. The doctor will also order a bone biopsy to obtain a sample of the tumor for examination in the lab. This is best done by an orthopedic surgeon experienced in the treatment of osteosarcoma (orthopedic oncologist).
Sometimes the doctor does a needle biopsy, using a long hollow needle to take a sample of the tumor. A local anesthesia is typically used in the area that's being biopsied. Alternatively, the doctor may order an open biopsy, in which a portion of the tumor is removed in the operating room by a surgeon while the child is under general anesthesia.
If a diagnosis of osteosarcoma is made, the doctor will order CT chest scans as well as a bone scan and, sometimes, additional MRI studies. These will show if the cancer has spread to any part of the body beyond the original tumor. These tests will be repeated after treatment starts to determine how well it is working and whether the cancer is continuing to spread.
Treating Osteosarcoma
Treatment of osteosarcoma in children includes chemotherapy (the use of medical drugs to kill cancer cells and shrink the cancer) followed by surgery (to remove cancerous cells or tumors) and then more chemotherapy (to kill any remaining cancer cells and minimize chances of the cancer coming back). Surgery often can effectively remove bone cancer, while chemotherapy can help eliminate remaining cancer cells in the body.
Surgical Treatment
Surgical treatments for osteosarcoma consist of either amputation or limb-salvage surgery.
Currently, most teens with osteosarcomas involving an arm or leg can be treated with limb-salvage surgery rather than amputation. In limb-salvage surgery, the bone and muscle affected by the osteosarcoma are removed, leaving a gap in the bone that is filled by either a bone graft (usually from the bone bank) or more often a special metal prosthesis. These can be appropriately matched to the size of the bone defect. The risk of infection and fracture is higher with bank bone replacement and therefore metal prostheses are more commonly used for reconstruction of the bone after removal of the tumor.
If the cancer has spread to the nerves and blood vessels surrounding the original tumor on the bone, amputation (removing part of a limb along with the osteosarcoma) is often the only choice.
When osteosarcoma has spread to the lungs or elsewhere, surgery may also be performed to remove tumors in these distant locations.
Chemotherapy
Chemotherapy is usually given both before and after surgery. It eliminates small pockets of cancer cells in the body, even those too small to appear on medical scans. A child or teen with osteosarcoma is given the chemotherapy drugs intravenously (through a vein) or orally (by mouth). The drugs enter the bloodstream and work to kill cancer in parts of the body where the disease has spread, such as the lungs or other organs.
Short-Term and Long-Term Side Effects
Amputation carries its own short-term and long-term side effects. It usually takes at least 3 to 6 months until a young person learns to use a prosthetic (artificial) leg or arm, and this is just the beginning of long-term psychological and social rehabilitation.
With a limb salvage surgery, one usually starts bending the knee or the affected body part almost immediately. A continuous passive motion (CPM) machine, that continuously bends and straightens the knee may be used to improve motion for tumors around the knee. Physical therapy and rehabilitation for 6 to 12 months following surgery usually enables the child to walk initially with a walker or crutches and then without any assistive devices. Early complications after surgery include infection and slow healing of the surgical wound, and the metal prosthetic device or the bank bone may need to be replaced in the long term. Other late problems might include fracture of the bank bone or failure of the bank bone to heal to the child's bone, which might require more surgery.
Many of the medications used in chemotherapy also carry the risk of both short-term and long-term problems. Short-term effects include anemia, abnormal bleeding, and increased risk of infection due to destruction of the bone marrow, as well as kidney damage and menstrual irregularities. Some drugs carry a risk of bladder inflammation and bleeding into the urine, hearing loss, and liver damage. Others may cause heart and skin problems. Years after chemotherapy for osteosarcoma, patients have an increased risk of developing other cancers.
Chances for a Cure
Recent studies have reported that survival rates of 60% to 80% are possible for osteosarcoma that hasn't spread beyond the tumor, depending on the success of chemotherapy.
Osteosarcoma that has spread cannot always be treated as successfully. Also, a child whose osteosarcoma is located in an arm or leg generally has a better prognosis than one whose disease involves the ribs, shoulder blades, spine, or pelvic bones.
New Treatments
Treatments are being developed and researched with new chemotherapy drugs. Other research is focused on the role certain growth factors might play in the development of osteosarcoma. This research may be used to develop new medications to slow these growth factors as a way to treat the cancer.
For osteosarcomas that cannot be removed surgically, studies are now underway to test treatments that use new combinations of chemotherapy and localized, high-dose radiation.