Osteosarcoma (OSA) is by far the most common bone cancer in dogs. Various bone cancers can also occur in cats, but the group that is significantly more susceptible to bone cancers is large and giant breed dogs. OSA can occur in any bone, but is most common in the long bones of the limbs, with the area of the carpus (wrist), stifle (knee) and shoulder being favorite spots.
Sadly, OSA’s are highly aggressive cancers and more than 90% would have spread elsewhere in the body such as the lungs, lymph nodes and other bones, by the time they are diagnosed. In addition to spread of the tumor, OSA in a bone will cause intense pain and lameness of the affected limb. Lameness is often the first sign noticed by owners, and is sometimes confused for other problems that cause lameness, such as fractures, ligament tears and arthritis.
Once the suspicion of OSA has been raised, the first step to diagnosis is x-rays of the bone. While some OSA’s are fairly obvious on x-rays, in some cases a biopsy may be required to confirm the diagnosis. Following diagnosis, the next step is staging of the disease. X-rays or a CT scan of the thorax (chest) and aspirates of the lymph nodes will be necessary to try to gauge spread of the cancer.
The first step to this cancer treatment in dogs is removal of the primary tumor via amputation of the limb or limb-sparing surgery. Many dogs manage to lead a fulfilling life following amputation, however this usually depends on the other three limbs being fairly functional. Chemotherapy is recommended following amputation, and about half of dogs that receive both treatments together survive for at least a year. If surgery is not an option, palliative medications may help make the remainder of the pooch’s life comfortable. Without treatment, the prognosis is very poor and the life-span is a matter of months.
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