Osteosarcoma stands out as the bone cancer type most commonly diagnosed in dogs. It is a very aggressive cancer with a high likelihood of metastasis, defined as a spread to other parts of the body.
Although it can be found in any breed and age of dog, osteosarcoma is most common in large breeds and older dogs. It typically originates in the bones of the leg, although in rare cases it may develop first in the vertebrae or the bones of the skull.
Dogs with osteosarcoma most often present with lameness, which is mild at first but worsens as the disease progresses. The disease can also cause swelling or discomfort, which tends to increase gradually unless the affected limb suffers a fracture. If this happens, the dog is likely to show sudden signs of severe pain.
The prognosis for a dog with osteosarcoma is generally poor, although there are treatments that can improve the dog's quality of life and even prolong life itself. Surgical amputation is the most common treatment, provided that the dog's remaining limbs are strong and free of disease, as dogs with these characteristics tend to adapt well to life with three legs. Dogs that cannot undergo amputation may be eligible for a limb-sparing procedure, although this is only an available option if the tumor is in an accessible location.
After the dog undergoes surgery, the veterinarian may recommend chemotherapy. This can extend the dog's life expectancy to as much as two years, as opposed to approximately 182 days with surgery alone. There are also a number of radiation treatments and other drugs that can reduce the pain associated with an osteosarcoma. As is true for all other treatments, selection of one or more of these drugs depends on a dog's individual needs.