Osteosarcoma in Dogs

Bone cancer is a common cancer in dogs. The most popular type of bone cancer is called Osteosarcoma (osteo = bone, sarcoma = cancer). It is a malignant tumour of bone and it is the most common bone tumour found in dogs. It mostly affects the limbs but it can also develop in the skull, spine and the ribs.

Osteosarcoma is most commonly found in large or giant breeds of dog. There are several scientific studies that correlate the development of this tumour with the weight and height of dogs and it is well known that certain dog breeds develop this tumour more often than others.

Reported predisposed breeds include Boxer Dogs, Doberman Pinschers, Golden Retrievers, German Shepherd Dogs, Great Danes, Great Pyrenees, Greyhounds, Irish Setters, Irish Wolfhounds, Labrador Retrievers, Rottweilers, Saint Bernards, and Weimaraners.

Osteosarcoma is an aggressive tumor and it can be assumed to have spread by the time it is first diagnosed; there is no possibility of preventing spread. That said, how well treatments can be expected to work depend on whether or not the tumor spread has progressed so as to be visible.

Causes

Current knowledge of the disease has not linked genetics or gender to the condition, but bone cancer does appear more often in large to giant breeds of dogs. Some studies have shown a slight increase in the development of osteosarcoma among dogs that have experienced a blunt bone injury.

Signs and Symptoms of Osteosarcoma in Dogs

The symptoms of osteosarcoma, or bone cancer, in dogs can be subtle. They may include:

• Lameness that doesn’t go away and swelling of the affected bone; these are the most common symptoms when a tumor affects a limb
• Swelling or a mass; this is often the first sign of a tumor in the skull, jaw, or ribs
• Difficulty eating if a tumor affects the jaw
• Neurologic signs, such as seizures or a wobbly gait, with the skull or spinal/vertebral tumors
• Breathing difficulties or lameness with rib tumors
• Loss of appetite and lethargy

How Osteosarcoma in Dogs is Diagnosed

If your vet suspects that your dog has developed bone cancer they will perform a physical and orthopedic examination of your pet and recommend an X-ray be done to look for signs of bone cancer.

If a possible tumor appears on the X-ray the area will biopsied for a definitive diagnosis. Blood tests, urinalysis, chest X-rays or a CT scan may also be performed to help assess your dog’s overall health and determine whether the cancer has spread to your pets respiratory system or other organs.

Treatment of Osteosarcoma in Dogs

The treatment of osteosarcoma almost always begins with amputation of the affected limb. Although many owners are understandably upset and concerned about amputating a limb, most dogs do very well with surgery. Because osteosarcoma is a painful disease, amputation also provides relief from unrelenting discomfort that is hard to control with pain medication alone. However, the prognosis remains poor with surgery alone; 90% of dogs will die of this disease within one year if surgery is the only treatment attempted.

Chemotherapy can help prolong remissions, with some dogs living years after amputation and chemotherapy. But these success stories tend to be the outliers, not the norm, and odds are still poor for long-term survival. Osteosarcoma spreads quickly, usually to the lungs, and nearly 90% of dogs have metastases by the time of diagnosis, even if there are no obvious signs of disease spread.