Osteosarcoma is a common bone cancer in large and giant breed dogs. It is uncommon in smaller dogs (and rare in cats). It usually affects the long bones of the legs, especially the front legs. Osteosarcoma is mostly, though not exclusively, a disease of older animals. It can be treated, but the disease is quite serious.
No genetic link has been confirmed, although Rottweilers do get osteosarcoma more often than any other breed. There is no known cause, and therefore no way to prevent the disease. Because osteosarcoma metastasizes, or spreads, quickly, it is very difficult to cure. Treatment usually focuses on keeping the dog comfortable for as long as possible.
How Is Osteosarcoma in Dogs Diagnosed?
The most common symptom of osteosarcoma is lameness, which might be intermittent. If you handle the affected leg, you might notice a sensitive area or a lump, but this is not always the case. The lameness can come on suddenly after vigorous exercise, or it can come on slowly. Generally, if a large dog starts limping for no apparent reason, you should call your vet.
At the vet’s office, an x-ray will be taken -- osteosarcoma often shows up as a Swiss cheese-like appearance in the bone. A needle biopsy confirms the diagnosis, though this can cause the dog more pain. Blood and urine samples will help your vet understand your dog’s overall health so you can make treatment decisions that are right for your dog. Your vet will probably also want to do a chest x-ray in order to check for metastases in the lungs, although x-rays cannot detect the smallest tumors. Because osteosarcoma spreads so easily, vets assume that metastases are present whether they can see them or not.
How Is Osteosarcoma Treated?
There are a couple of different options for treating osteosarcoma, depending on your dog’s overall health. The standard treatment is amputation of the affected leg in order to remove the primary tumor, followed by systemic chemotherapy in order to attack any secondary tumors. Sometimes it is possible to remove the tumor without amputating the leg, but the loss of a leg does not seriously disable most dogs. Occasionally, this combination of surgery and chemotherapy results in a complete cure. More often, it simply buys time and makes the patient more comfortable.
Some dogs are not candidates for surgery because they have severe arthritis in the other limbs or other medical problems. Some people elect not to do chemotherapy because of the expense or for other reasons. Surgery without chemotherapy cannot cure osteosarcoma, but it does lessen the dog’s pain. Chemotherapy without surgery does not do much good. For dogs who cannot have surgery, radiation treatment can slow the disease and relieve pain. Any dog with an osteosarcoma diagnosis should also receive pain medication.
What Is the Outlook for My Dog?
Osteosarcoma is a serious disease. A cure is possible, but unlikely. What you can do is make the months or years your dog has left as good as possible. Bone cancer is a very painful disease, so treatment is about relieving pain, even more than it is about extending life. Amputation might seem like a drastic step, but most dogs adapt to the loss of a leg very well, and removing the primary tumor means the relief of pain.
Half of all dogs treated for osteosarcoma with surgery and chemotherapy live at least one more year. A quarter live at least two more years. Two years is a short time for us, but it is a long time for a dog. If those extra months or years are good, happy years, you have fought for your friend and you have won.
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