Osteosarcoma In Dogs

Perhaps one of the hardest parts of being a veterinarian is when a diagnosis with a poor prognosis is made. Delivering bad news to an owner is hard for the nurses, doctors, and everyone involved in the case. One such example is a disease called osteosarcoma, a cancer of the bone. In the following article, I will discuss how a diagnosis of Osteosarcoma is made as well as treatment options available.

A sarcoma is a cancer that has originated from a connective tissue stem line. Connective tissue can be thought of as the supporting matrix that holds the bodies tissues together Bone, blood, cartilage, ligaments, fat, and a few others can all be considered connective tissue. Osteo literally means relating to the bones. So, a diagnosis of Osteosarcoma is a cancer of the connective tissue type, bone. It is the most common primary cancer of the bone of dogs and cats although there are others. Osteosarcomas are much more common in large and giant breed dogs although any breed of dog or cat can be affected.

There’s a saying in veterinary medicine that Osteosarcomas tend to develop away from the elbow and towards the knee. The most common site is of the lower portion of the radius, just above the joint in humans that would be called the wrist joint. Osteosarcomas also tend to develop at the top of the humerus, close to the shoulder joint and near the knee of a hind limb. While small breed dogs are much less likely to get this form of cancer when they do it tends to occur on the axial spine.

When cancer affects the bone, it destroys the normal tissue in the process. What results is swelling, heat, pain, and loss of function. Sometimes an owner is just taking their dog on a normal walk when they suddenly appear to break their leg with no inciting trauma or injury to cause it. The reason this occurs is that the cancer has eaten away the normal bone leaving the area easily susceptible to fracture. The resulting pain and swelling often times results in the patient not using the affected leg.

A diagnosis of Osteosarcoma is usually made by taking radiographs (x-rays) of the affected area along with Physical Examination findings. It is a fairly straightforward diagnosis from plain x-ray films. Cancer eating the bone can be seen readily, leaving what we call a “lytic” or “moth-eaten” pattern. Others refer to this pattern as “star-bursts” because it looks like how a child might draw rays extending out from the sun.

Unfortunately, bone cancer is an aggressive form of disease and treatment is aimed at slowing its spread and limiting or alleviating associated pain. To date, there is no known absolute cure for Osteosarcoma and by the time a diagnosis is made, at least a few cancer cells have escaped the affected limb. For this reason, sometimes amputation is recommended to relieve pain, suffering, and to slow the spread of cancer. Amputation is a recommended treatment but it will not permanently cure the disease. Other treatment options aimed at slowing the progression of cancer center around chemotherapy options

The prognosis for patients with Osteosarcoma is poor, with median survival times of around 4 months reported with amputation. Less than 10% of dogs affected with Osteosarcoma have a 1 year or greater survival rate. However, new treatment options are being studied now which may give us new hope in the fight against this terrible disease. Dr. Nicola Mason at the University of Pennsylvania is working a new type of treatment. By stimulating the immune system to fight the cancer cells directly, Dr. Mason and her team are working on an Osteosarcoma Vaccine to fight the disease once diagnosed. (Source: www.vet.upenn.edu/research/centers-intiatives/mason-immunotherapy-research/therapies-trials/canine-osteosarcoma)

Bone Cancer in Dogs

If you notice any changes to your dog’s leg or legs, including swelling, heat, pain, or decreased function we recommend scheduling an examination with a member of our veterinary team. Whether it’s a sprain, fracture, Ligament Tear, or the dreaded Osteosarcoma, early diagnosis leads to early treatment, less pain and suffering, and better outcomes. To schedule an appointment or speak to a member of our Veterinary Team, please call one of our offices.

Jeffrey Stupine
Medical Director
World of Animals Veterinary Hospitals