a senior dog laying in the grass

Osteosarcoma (OSA), the most common bone cancer, represents about 85% of bone tumors in dogs. These aggressive tumors spread rapidly, and once diagnosed, should be taken very seriously.

“OSA commonly affects the limbs of large or giant breed dogs, but can also occur in other parts of the skeleton, such as the skull, ribs, vertebrae, and pelvis,” said Dr. Rita Ho, veterinary intern instructor at the Texas A&M College of Veterinary Medicine & Biomedical Sciences.

Dogs with limb osteosarcoma typically show signs of swelling at the affected side and associated lameness, depending upon the animal’s unique condition and tumor location. The tumors typically form at or near growth plates, and occasionally, the animal will exhibit a growth on their body or painful inflammation near the site of the tumor. If swelling does exist, it is likely due to extension of the tumor into the surrounding tissues.

Diagnosis of osteosarcoma is begun with orthopedic and neurologic examinations, a physical examination, and various x-rays. “The biological behavior, prognosis, and treatment of osteosarcoma depend of the primary site, and extent of the disease,” said Dr. Ho. “Therefore, various diagnostic tests such as radiographs (X-rays), blood tests, and sometimes a biopsy or fine needle aspirate are required to determine the most appropriate treatment.”

Depending on your pet’s specific condition, there are various treatment options you can consider, including surgery, chemotherapy, and radiation. “Limb OSA commonly causes lameness and pain because of invasion and destruction of normal bone; therefore surgery is usually the first recommendation,” said Dr. Ho. “The surgery serves two purposes: it removes the primary tumor, which is necessary for cancer control, but it also removes the source of pain and may therefore dramatically improve quality of life.”

Surgery often involves amputation of the diseased limb, which completely resolves the pain for your pet. However, for people who are reluctant to have this procedure done, there are other surgical methods to spare the limb if your pet is not a good candidate or if you aren’t comfortable with the surgery. Just keep in mind that amputation is almost always well tolerated with the dogs, and a 3-legged dog can do virtually everything 4-legged dogs can.

Chemotherapy is administered to a pet following amputation to kill off any remaining cancer cells, and radiation is recommended primarily for relieving bone pain and discomfort. “The average dog with OSA will live only four months if treated with only surgery,” said Dr. Ho. “With chemotherapy following surgery, usually the life expectancy is 10-12 months.”

As with any surgery, activity and mobility after the operation will be restricted and pain management programs as well as various medications are typically prescribed for the animal after surgery. However, it is important to remember that you should never administer any pain medication without first consulting your veterinarian.

Unfortunately, osteosarcoma in dogs has not been found to be preventable. With thorough examinations and early recognition of the symptoms, however, it can be caught soon enough to take the necessary measures to stop the cancer from spreading and to keep your pet healthy and happy for as long as possible.

Pet Talk is a service of the College of Veterinary Medicine & Biomedical Sciences, Texas A&M University. Stories can be viewed on the Web at vetmed.tamu.edu/news/pet-talk. Suggestions for future topics may be directed to editor@cvm.tamu.edu.

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