Bone cancer in dogs, or osteosarcoma, is an aggressive cancer that often requires amputation of the affected limb. Osteosarcomas account for as many as 90% of all canine bone cancers. They're found most often in large breed dogs and can be difficult to treat.
Risk Factors for Osteosarcoma
Elderly large breed dogs are at the highest risk for developing canine osteosarcomas. Some breeds are more vulnerable to this disease than others. Breeds with a genetic predisposition to osteosarcomas include:
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Great Pyrenees
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Newfoundlands
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German Shepherds
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Weimaraners
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Boxers
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Rottweilers
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Bernese Mountain Dogs
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Saint Bernards
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Great Danes
Dogs that weigh more than 80 pounds are in the highest risk group. Small dogs rarely develop this type of tumor. Male dogs, geriatric dogs and dogs between one and two years of age are most vulnerable to bone cancer.
Vets don't know exactly what causes bone cancer in dogs, but they believe that the cells found on the bone growth plates are prone to mutate easily. Fracture or other bone trauma may contribute to the development of the disease.
Symptoms of Canine Osteosarcoma
The symptoms of bone cancer in dogs might vary slightly depending on where the tumors appear. Most bone cancer tumors appear in the long bones of the limbs, in the vicinity of the knee or near the elbow. Tumors may cause joint pain and lameness in the leg.
By the time of diagnosis most cases of canine osteosarcoma have already spread to the lungs or other organs. Osteosarcoma tumors in the lungs may be so small that they won't show up on X-rays at first. Because cancer spreads to the lungs in more than 90% of cases of bone cancer in dogs, your vet may proceed as if this has already happened, whether he can find proof or not. Your vet will perform a biopsy of any tumors he may find on X-rays, to determine whether or not the masses are cancerous.
Diagnosing Canine Bone Cancer
Tumors in the bones, lungs and other organs will be visible on X-rays. Many dogs with bone cancer receive a diagnosis after suffering severe degeneration of the affected bones and joints. Bone cancer in dogs often causes bones tissue to deteriorate and this can lead to fractures that will never heal.
If your vet suspects osteosarcoma, he may also check for fungal infections of the bones. These can produce symptoms similar to bone cancer.
Treating Bone Cancer in Dogs
Osteosarcoma is a very aggressive dog cancer, usually requiring amputation of the diseased limb. Following surgery, your dog will need a round of chemotherapy to treat any tumors that may have spread to the lungs and other organs. Chemotherapy can also help prevent the recurrence of bone cancer. If your dog receives successful treatment, he could live for a year or more following diagnosis.