Osteo is Latin for bone, and sarcoma means a malignancy (cancer) of the connective tissue so Osteosarcoma is a cancer of bone cells. There are many types of cancer that can form in bones but osteosarcoma (also referred to as OGS) is the most common type that occurs in children and adolescents, coinciding with time in a child’s life when they are going through a growth spurt.1 It is a rare cancer, with less than 500 new cases diagnosed in the U.S. each year. OGS most commonly affects the larger bones of the upper arm (humerus), thigh (femur) and lower leg (tibia) but it can affect all other bones of the skeleton.
SIGNS AND SYMPTOMS OF OSTEOSARCOMA
- Pain – the pain a child experiences is typically in the area of the tumor and is referred to as local pain.
- Swelling – there may be inflammation in the area of a tumor leading to swelling.
- Decreased function – pain and swelling lead to a child “favoring” the affected extremity so he or she may not want to put weight on it or use it in any way.
- Fracture – the area of the bone where the tumor is located is weaker and more fragile than normal bone so fractures (called pathologic fracture) can occur in this area of the bone tumor.
CAUSE OF OSTEOSARCOMA
In most instances there is no direct cause of osteosarcoma. There are some conditions that place someone at a higher risk of developing osteosarcoma. These include:
- Previous treatment using radiation therapy.
- Hereditary conditions:
DIAGNOSTIC TESTS FOR OSTEOSARCOMA
The first test that raises suspicion for osteosarcoma is an x-ray. When there is an osteosarcoma present the x-ray often shows an area with a ‘sunburst’ type pattern in the region where a child is experiencing the pain. This pattern is caused by the cancerous bone-forming cells, producing bone in a non-functional manner. Once a bone tumor is suspected it is very important that an orthopedic oncologist is consulted before further testing or biopsy.
Because this is a rare condition, it is best managed by specialists who have training and experience in diagnosing and treating extremity sarcomas.
|MRI ||An MRI enables the doctors to better see the full extent of the tumor. It’s important to know if the tumor is ‘invading’ other tissues as treatment plans (such as surgical options) are being considered.|
|Biopsy||A biopsy is necessary to determine the exact type of tumor and its grade (aggressiveness). The biopsy should be done by a specialist experienced in appropriate biopsy of extremity tumors because they are well-versed in biopsy techniques. A biopsy done incorrectly may limit surgical options, and in some cases make amputation the only surgical option.|
Tumor grades include: Low-grade
|Bone scan||A bone scan is one of the tests done to help determine the extent of the cancer (staging). This is like an x-ray of your entire skeleton to see if there are any other areas of tumor.|
|PET/CT scan||This test is another that is necessary for the staging of the cancer. It reveals if the cancer has metastasized to the abdomen, brain or other areas of the body|
OSTEOSARCOMA GRADE AND STAGING
It is important to know how aggressive a tumor is (the grade of the tumor) as well as the stage of the cancer (has it spread to other areas of the body). This information helps the physicians in determining the best approach to treatment, as well as assisting in discussions about prognosis.
Osteosarcoma Grade – when a pathologist looks at the tumor tissue under a microscope they can determine if the tumor has the tendency to grow quickly and spread. Osteosarcoma grades are:
|Low grade||less likely to spread (metastasize)|
|Intermediate grade||moderately aggressive so may spread to other areas|
|High grade||more aggressive so likely to metastasize|
Osteosarcoma Stage – stage combines the information from the diagnostic testing to determine the extent or severity of the disease process. The size of the tumor, if it has spread to other area such as the lungs, brain, or other bones, as well as the grade are all considered when determining the stage. OGS staging is from I (one) to III (three) with stage I meaning the tumor is localized (only in the original site) and stage III indicating that the tumor has metastasized to other areas of the body.
TREATMENT OF OSTEOSARCOMA
Once the diagnosis of bone cancer has been made and staging of the tumor is completed, treatment is started. Through many years of research, specialists have determined that the most effective course of treatment involves chemotherapy before surgery (neoadjuvant chemotherapy), followed by surgical resection of the tumor, and followed by a course of postoperative chemotherapy (adjuvant chemotherapy). Radiation has not been shown effective in treating primary osteosarcoma so it is rarely used.
Chemotherapy – “Chemo” is the use of medications to kill cancer cells and for treatment of bone cancer it is given systemically, meaning the medications enter the bloodstream and reach the cancer cells.
Depending on the treatment center, chemotherapy is given through the artery (intra-arterial) or through the vein (intravenous). Chemotherapy for OGS involves multiple courses of administration, for example the medications may be given once a week for several weeks.
Surgery – once the chemotherapy course is completed surgery is necessary to remove the bone tumor. It is very important that the entire tumor is removed in order to minimize the possibility that the tumor will return; therefore, the surgeon will remove a small amount of normal tissue around the tumor to better assure that no cancerous cells are left. Very careful surgical planning is necessary to accomplish complete removal (resection) of the bone tumor and maintenance of the patient’s best function.
Options can include:
|Resection||Removal of the tumor without “rebuilding” the area that the tumor was removed from, more common in pelvic tumors than tumors in the extremity|
|Resection with reconstruction||Removal of the tumor and “rebuilding” with metal implants and/or bone allografts; soft tissue reconstruction may also be necessary|
|Amputation||Removing the extremity at a level above the tumor|
“What’s the chance of recovery?”……This is one of the first questions that we asked when faced with a challenging diagnosis. This is true regardless of age, but especially when kids are diagnosed with any type of cancer.
Prognosis means ‘chance of recovery’ and there are factors that contribute to the prognosis of osteosarcoma.
Tumor site – the location of the tumor and whether there are tumors in more than one bone. Tumors in a location further from the center of the body have a better prognosis than those closer to the center of the body. Tumors in more than one bone indicate there has been metastasis or a more aggressive form of osteosarcoma.
Presence of metastatic disease – the stage of cancer at the time of diagnosis contributes to prognosis. If the disease has spread to the lungs or other sites the prognosis it is not as good.
Size of the tumor – larger tumors has a worse prognosis.
Response to initial chemotherapy – when the tumor is resected during surgery it is tested to determine how much of the tumor died (indicating that the chemotherapy was effective). If the amount of necrosis (tissue death) is greater than 90% the prognosis is better.
Surgical resection – if the tumor is resected and the surgeon is able to remove the tumor with a “layer” of non-affected tissue around it there is less chance that cancer is still in the area.
In general, the long-term survival of kids diagnosed with osteosarcoma is ~70%1. It’s important to keep in mind that this estimate is determined by examining survival information for all kids diagnosed with osteosarcoma in a certain time frame, regardless of the prognostic factors described above. There are reports of survival from 80 – 92% 2, 3 in patients grouped by stage of disease when first diagnosed. It is important to discuss the prognosis with your child’s doctor to be sure you understand the stage of the disease and how it relates to treatment and diagnosis.
1. Mirabello L, Troisi RJ, Savage SA: Osteosarcoma incidence and survival rates from 1973 to 2004: data from the Surveillance, Epidemiology, and End Results Program. Cancer 115 (7): 1531-43, 200
2.Bacci G, Balladelli A, Palmerini E, Alberghini M, Pollastri P, Galletti S, Mercuri M, Picci P., Neoadjuvant chemotherapy for osteosarcoma of the extremities in preadolescent patients: the Rizzoli Institute experience. J Pediatr Hematol Oncol. 2008 Dec;30(12):908-127
3. Wilkins RM, Cullen JW, Camozzi AB, Jamroz BA, Odom L;Improved survival in primary nonmetastatic pediatric osteosarcoma of the extremity. Clin Orthop Relat Res. 2005 Sep;438:128-36</strong<=>