Diagnosing & Treating Osteosarcoma In Dogs Bone Cancer In Giant Breed Dogs

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Osteosarcoma is a bone cancer that is usually found more so in large breed dogs than in small dog breeds and cats. When your dog is diagnosed with cancer, it is important to learn as much as you can in order to get them the proper care and treatment needed. Learn more here.

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 vetโ€™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 dogโ€™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 dogโ€™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 dogโ€™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.

Osteosarcoma In Dogs And Cats

Osteosarcoma, or OSA, is the most common bone tumor found in dogs. This type of cancer can also occur in cats, but it is far less common. In dogs, osteosarcoma is very aggressive and tends to spread rapidly to other parts of the body, making early detection and treatment incredibly important. Here weโ€™ll review causes and symptoms so that youโ€™ll know what to look out for, as well as treatment options so youโ€™ll know what to expect.

Causes of Osteosarcoma in Dogs and Cats

The causes of osteosarcoma in dogs and cats are not well understood. What we do know is that middle-aged to older large and giant breed dogs are the most widely affected.
Osteosarcoma can occur in any bone in the body, though in dogs, most tumors appear in the front limbs near the โ€œwrist.โ€

Symptoms of Osteosarcoma in Dogs and Cats

The symptoms of bone cancer can be subtle, and may include lameness, swelling or a lump near the tumor site, bone or joint pain, lethargy, and loss of appetite.
Lameness is certainly the most common symptom and often the most obvious as well. A dog may experience sudden lameness (for example, following strenuous exercise or jumping off the bed) or the lameness may develop more slowly.

Diagnosing Osteosarcoma in Dogs and Cats

Many pets end up at the vetโ€™s office after their owner notices lameness that is not resolving. The symptom is investigated with a radiograph, which will reveal a problem area if osteosarcoma is present. In order to reach a definitive diagnosis, the problem area must be biopsied. However, not all veterinarians perform this procedure; in some cases, the results of the radiograph will be suggestive enough to assume a diagnosis.
In addition, chest x-rays, blood testing, and a urinalysis will be performed to assess the petโ€™s overall health. In most dogs (around 90 to 95%), the tumor will have already metastasized (spread) at the time of diagnosis. Osteosarcoma tumors most commonly spread to the lungs, but this rarely shows up during testing as the metastatic tumors are initially microscopic. However because of the high incidence of metastasis, most pets are treated for it regardless of what testing reveals.

Treatment for Osteosarcoma in Dogs and Cats

Because osteosarcoma tumors are very likely to spread, the most common treatment is amputation of the affected limb followed by chemotherapy to treat existing metastasis or metastasis that canโ€™t yet be seen. For many owners, amputation is a difficult decision, and not all pets are candidates (for example, dogs with severe arthritis in the affected limb). However amputation is a good option for many other dogs, and dogs with three legs can actually function very well.
If the dog is not a candidate for amputation, or if the owner decides that they do not want to go through with it, the only other option is palliative care. Palliative care aims only to make the animal more comfortable; it does not solve the underlying problem. Common palliative treatments include radiation therapy and drugs (analgesics) to reduce pain. Pets treated with palliative care tend to survive only 6 months before they succumb to the cancer or require euthanasia.


The prognosis for pets with osteosarcoma depends on the severity and spread of the disease as well as the treatment carried out. Pets who undergo amputation and chemotherapy tend to have a fair-to-good prognosis, and some pets are even completely cured. As mentioned above, pets that receive only palliative care survive an average of 6 months. Your veterinarian will help you determine the best course of treatment for your pet.

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