BONE CANCER (Osteosarcoma)
Osteosarcoma is a primary cancer of the bone. It destroys normal bone, leaving in its place abnormally brittle and fragile bone prone to fracture. Osteosarcoma is an aggressive cancer that spreads rapidly to other parts of the body, usually long before it is even detected.
Large and giant breed dogs have the greatest incidence of bone cancer in their limbs. The Rottweiler In particular seems to be over-represented as a common breed predisposed to bone cancer. The average age of dogs with osteosarcoma is 7 years. Males are more commonly affected than females. Smaller dogs — and cats — can also get bone cancer, but this is much rarer.
Osteosarcoma is a terminal disease. There is no cure. The mean life expectancy of a dog with osteosarcoma is approximately 3 to 4 months. See Treatment Options.
Symptoms can be difficult to recognise and easy for an owner to confuse with less serious issues. Dogs affected with appendicular tumours are often lame. Sometimes the limb is enlarged and firm, as well as painful. Less commonly they may be reluctant to eat or walk and can sometimes bleed from the tumour surface.
Osteosarcoma can spread quickly to the lungs and other organs so coughing and breathing difficulties are a long term complication. In about 80 per cent of cases, by the time the owner realises something is wrong and brings their pet to the hospital, it has metastasized to the lungs or heart.
While an early diagnosis cannot help us stop the cancer it can assist us in helping to control the pain and make your pet’s last months more bearable. It is worth owners being aware that what looks like a simple limp can in fact indicate something much more serious and always needs checking out.
Digital Radiography is the primary diagnostic tool. Radiographic signs of osteosarcoma include cortical lysis — where the outer margins of the bone start to dissolve —periosteal bone proliferation, which makes the edges of the bone look blurry on the radiograph, and soft tissue swelling.
Radiography does not always provide a confirmed diagnosis but when assessed with the history of the pet, its age and breed it does make a bone cancer diagnosis more likely. CT scans can provide a more accurate diagnosis but are rarely necessary to confirm Osteosarcoma.
Bone cancer is very painful and the patient will need powerful pain relief on a daily basis throughout their last months. Surgical intervention — usually the amputation of an affected limb — is possible, but amputation does not necessarily prolong the animal’s life, although it does make the pain more bearable.
Chemotherapy can extend the life span of most dogs suffering bone cancer, by approximately one year. They will then usually sucumb to the illness, or need to be euthanised for humane reasons. The drugs used in chemotherapy are powerful and aggressive and, generally, come with a cost to the dog’s quality of life.