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Osteosarcoma

Osteosarcoma is the most common type of primary bone cancer in dogs accounting for up to 85% of tumors that originate in the skeletal system. It is estimated that at least 6,000 new cases, and perhaps even more than 8,000, are diagnosed in dogs each year in the United States. Osteosarcomas are seen most often in the appendicular skeleton (long bones of the limbs), most often “near the knee” and “away from the elbow.” However, these tumors can also affect the axial skeleton (cranium, spinal column, ribs). Large and giant breed dogs are at higher risk for bone cancer, especially of the long bones. For example, it is estimated that the relative risk to develop this disease in giant breeds such as Scottish Deerhounds and Great Danes may be as much as 200-times higher than in small and toy breeds. Among dogs at high risk, we also include Rottweilers, Great Pyrenees, Greyhounds, Mastiffs, and others. The disease usually becomes evident during middle age (~7-10 yr), although bone cancer can affect dogs under 1 year of age. Factors that affect growth rate, such as diets that promote rapid growth in puppies, also appear to influence risk. The tumors are very aggressive and metastatic, so it is a fair assumption that at the time of diagnosis the disease will have already spread beyond the primary site. For this reason, the standard-of-care for bone cancer includes surgery to remove the primary tumor, followed by adjuvant chemotherapy to attack the cells that have left the site. In dogs, approximately 50% survive one year with standard-of-care, less than 30% survive 2 years, and less than 10% reach 3 years. These statistics are tempered when we consider that one year is approximately 10% of a canine lifetime; however, we feel that new therapies designed to exploit the genetic and biochemical abnormalities of the tumors will help us improve the outcome of dogs with this disease.