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Osteosarcoma is the most common type of malignant bone cancer, accounting for 35% of primary bone malignancies. There is a preference for the metaphyseal region of tubular long bones. 50% of cases occur around the knee. It is a malignant connective (soft) tissue tumor whose neoplastic cells present osteoblastic differentiation and form tumoral bone.
Additional recommended knowledge
Osteogenic Sarcoma is the 6th leading cancer in children under age 15. Osteogenic Sarcoma affects 400 children under age 20 and 500 adults (most between the ages of 15-30) every year in the USA. Approximately 1/3 of the 900 will die each year, or about 300 a year. A second peak in incidence occurs in the elderly, usually associated with an underlying bone pathology such as Paget's disease, medullary infarct, or prior irradiation. Although about 90% of patients are able to have limb-salvage surgery, complications, such as infection, prosthetic loosening and non-union, or local tumor recurrence may cause the need for further surgery or amputation.
The tumor may be localized at the end of the long bones. Most often it affects the upper end of tibia or humerus, or lower end of femur. The tumor is solid, hard, irregular ("fir-tree" 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 Codman's triangle. Surrounding tissues are infiltrated.
Microscopically: The characteric feature of osteosarcoma is presence of osteoid (bone formation) within the tumour. Tumor cells are very pleomorphic (anaplastic), some are giant, numerous atypical mitoses. These cells produce osteoid describing irregular trabeculae (amorphous, eosinophilic/pink) with or without central calcification (hematoxylinophilic/blue, granular) - tumor bone. Tumor cells are included in the osteoid matrix. Depending on the features of the tumour cells present (whether they resemble bone cells, cartilage cells or fibroblast cells), the tumour can be subclassified.
The causes of osteosarcoma are not known. Questions remain about whether radium, or fluoride, in drinking water can act as "environmental triggers" for increasing the incidence of the disease. A low selenium or Vitamin D3 level or a high level of inflammation, as measured by interleukin-6, interleukin-8, or Nf-kB, Tumor Necrosis Factor Alpha may have a significant role as tumor suppressors and tumor initiators respectively. Recent studies show that an increased level of c-Fos can lead to osteosarcoma. The study that showed this result was done on transgenic mice in which the Fluid Sheer Stress (FSS) was increased to increase the number of osteoblast. Since c-Fos is ubiquitous in its overexpression it can not only increase the osteoblast resulting in the symptoms osteosarcoma. Therefore it is recently believed that a biological effect that may cause osteosarcoma is an error in the molecular pathway that controls c-Fos, causing an overexpression with no other counter stimuli to stop over production
Many patients first complain of pain that may be worse at night, and may have been occurring for some time. If the tumour is large, it can appear as a swelling. The affected bone is not as strong as normal bones and may fracture with minor trauma (a pathological fracture).
Family physicians and orthopedists rarely see a malignant bone tumor (most bone tumors are benign). Thus, many patients are initially misdiagnosed with cysts or muscle problems, and some are sent straight to physical therapy without an x-ray.
The route to osteosarcoma diagnosis usually begins with an x-ray, continues with a combination of scans (CT scan, PET scan, bone scan, MRI) and ends with a surgical biopsy. Much can be seen on films, but the biopsy is the only definitive proof that a bone tumor is indeed malignant or benign.
The biopsy of suspected osteosarcoma should be performed by a qualified orthopedic oncologist. The American Cancer Society states: "Probably in no other cancer is it as important to perform this procedure properly. An improperly performed biopsy may make it difficult to save the affected limb from amputation."
Patients with osteosarcoma are best managed by a medical oncologist and an orthopedic oncologist experienced in managing sarcomas. Current standard treatment is to use neoadjuvant chemotherapy (chemotherapy given before surgery) followed by surgical resection. The percentage of tumor cell necrosis (cell death) seen in the tumor after surgery gives an idea of the prognosis and also lets the oncologist know if the chemotherapy regime should be altered after surgery.
Standard therapy is a combination of limb-salvage orthopedic surgery and a combination of high dose methotrexate with leucovorin rescue, intra-arterial cisplatin caffeine, adriamycin, ifosfamide with mesna, BCD, etoposide, muramyl tri-peptite (MTP).
Ifosfamide can be used as an adjuvant treatment if the necrosis rate is low.
3-year event free survival ranges from 50% to 75%. and 5-year survival ranges from 60% to 85+% in some studies. Overall, 60-65% treated 5-years ago (2000) will be alive today. Osteosarcoma has one of the lowest survival rates for pediatric cancer despite chemotherapy's success in osteosarcoma of 6 chemotherapies, interferon-alpha, interleukin-2, and being the prototype of solid tumors in cancer.
Fluids are given for hydration.
Blood helps with anemia.
Best treatment protocols
Top 5 treatment protocols are ranked here by osteosarcoma support
Osteosarcoma is the most common bone tumor in dogs and typically afflicts middle-age large and giant breed dogs such as Irish Wolfhounds, Greyhounds, German Shepherds, Rottweilers, and Great Danes. It has a ten times greater incidence in dogs than humans. A hereditary base has been shown in St. Bernard dogs. Spayed/neutered dogs have twice the risk of intact ones to develop osteosarcoma. Infestation with the parasite Spirocerca lupi can cause osteosarcoma of the esophagus.
The most commonly affected bones are the proximal humerus, the distal radius, the distal femur, and the tibia, following the basic premise "far from the elbow, close to the knee". Other sites include the ribs, the mandible, the spine, and the pelvis. Rarely, osteosarcoma may arise from soft-tissues (extraskeletal osteosarcoma). Metastasis of tumors involving the limb bones is very common, usually to the lungs. The tumor causes a great deal of pain, and can even lead to fracture of the affected bone.
Treatment and prognosis
Amputation of the leg is the initial treatment, although this alone will not prevent metastasis. Chemotherapy combined with amputation improves the survival time, but most dogs still die within a year. There are surgical techniques designed to save the leg (limb-sparing procedures), but they do not improve the prognosis. One key difference between osteosarcoma in dogs and humans is that the cancer is far more likely to spread to the lungs in dogs.
Some current studies indicate that osteoclast inhibitors such as alendronate and pamidronate may have beneficial effects on the quality of life by reducing osteolysis, thus reducing the degree of pain as well as the risk of pathological fractures.
Osteosarcoma in cats
Osteosarcoma is also the most common bone tumor in the cat, although not as frequently encountered, and most typically affects the rear legs. The cancer is less aggressive in cats than in dogs, and therefore amputation alone can lead to a significant survival time.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Osteosarcoma". A list of authors is available in Wikipedia.|