November is National Pet Cancer Awareness Month. According to the National Cancer Institute, one in ten dogs will have a new diagnosis of cancer in any given year. The numbers for cancer in cats are similar. This blog post will focus on osteosarcoma or bone cancer.

Diagnosing Osteosarcoma

Osteosarcoma is the most common tumor of the bone in dogs. It can occur in any bone in the body, but the most significant form of the disease occurs in the legs. The first sign of the tumor is often limping. You may notice a firm, painful, swelling on the bone during a big cuddle session. Occasionally, the first sign of osteosarcoma is a fractured leg without any known traumatic accident like being hit by a car or falling from a height. Any dog or cat can develop osteosarcoma, but large and giant dog breeds develop this tumor at a higher rate than small dogs.

X-rays are a good tool in the diagnosis of osteosarcoma. The x-ray accompanying this blog shows an osteosarcoma of the thigh bone (femur) of a dog. The tumor causes the bone in the center of the x-ray to have a mottled or moth-eaten appearance. The portion of the femur closer to the top of the x-ray is normal. If you squint really hard at the x-ray, you can see a circular swelling around the bone that was the lump the owners felt.

Treating Canine Osteosarcoma

As you can tell from looking at the x-ray, the tumor encompasses a large portion of the bone and cannot be removed while maintaining limb function. Since dogs and cats can manage “three legs and a spare,” amputation of the leg is the most common treatment for canine osteosarcoma. Limb sparing surgery, where the tumor is removed and donor bone is implanted, is an option with an osteosarcoma in just the right location. Prosthetic legs are gaining popularity among veterinary patients, but they may not be quite right for every dog or cat undergoing amputation.

Osteosarcoma is a tenacious tumor. Even with a serious surgery like amputation, tumor cells find away to metastasize throughout the body. In dogs, veterinary oncologists at AMC prescribe post-operative chemotherapy to delay the spread of the osteosarcoma throughout the body.

Feline Osteosarcoma

The osteosarcoma story is mostly the same in cats, with two major differences. First, osteosarcoma occurs less often in cats than in dogs, but still occurs most commonly in the bones of the legs.  Osteosarcoma does not appear to metastasize as often in cats than in dogs. This second difference between canine and feline osteosarcoma means chemotherapy is not always recommended for cats following amputation.

Canine Osteosarcoma and One Health

Interestingly, canine osteosarcoma plays important role in human oncology. Because osteosarcoma occurs more frequently in dogs than humans, treatments tested in dogs can lead to improvements in the treatment of human osteosarcoma. Osteosarcoma is an active area of clinical research in veterinary patients. If you are interested in a clinical trial for your pet, search the Animal Health Studies Database for clinical trials currently accepting patients.