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 and treatment options available.
A sarcoma is cancer that has originated from a connective tissue stem line. Connective tissue can be conceived as the supporting matrix that holds the body’s tissues together. Bone, blood, cartilage, ligaments, fat, and a few others can all be considered connective tissue. Osteo 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 significantly more common in large and giant breed dogs, although any dog or cat breed can be affected.
There’s a saying in veterinary medicine that Osteosarcomas 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 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, it tends to occur on the axial spine when they do.
When cancer affects the bone, it destroys the normal tissue in the process. The results of this are swelling, heat, pain, and loss of function. Sometimes an owner is just taking their dog on a regular walk when they suddenly appear to break their leg with no inciting trauma or injury to cause it. This occurs because the cancer has eaten away the normal bone, leaving the area easily susceptible to fracture. The associated pain and swelling often result 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. The 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 how a child might draw rays extending from the sun.
Unfortunately, bone cancer is an aggressive form of disease, and treatment aims to slow its spread and limit or alleviate 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 four months reported with amputation. Less than 10% of dogs affected with Osteosarcoma have a one-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 on a new type of treatment. By stimulating the immune system to fight 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, reduced 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 V.M.D.
World of Animals Veterinary Hospitals