Osteosarcoma (OSA) is an aggressive cancer of bone that most frequently affects older, large breed dogs. The legs are the most common site for the development of an osteosarcoma, but any bone can be affected.
Osteosarcomas are very painful, so when the cancer is located in a leg, the first problem that owners generally notice is limping. A firm swelling may also be felt at the site of the tumor. Veterinarians can diagnose most cases of the disease based on an animal's symptoms, physical exam, and x-rays. In some cases, a biopsy may be necessary to differentiate osteosarcoma from other diseases (e.g., bone infections or other types of cancer) that cause similar clinical signs and changes that are visible on x-rays.
The most important aspect of treatment for an osteosarcoma is pain relief. Surgery to remove the cancerous portion of bone is the best way to eliminate the intense discomfort associated with this disease. Typically, the affected limb is amputated, but surgical procedures that allow the patient to keep its leg are also available. If surgery is not practical, radiation therapy can provide relief in some cases. Pain relieving medications are also an important component of treatment for osteosarcoma. This type of cancer rapidly spreads throughout the body, and chemotherapy is necessary to significantly extend an animal's life expectancy after surgery. However, even with chemotherapy, most dogs with osteosarcoma do not live more than a year or two after diagnosis.
Written by: Jennifer Coates, DVM
Last reviewed: October 2, 2008