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Osteosarcoma | Bone Cancers That Affect Dogs

Picture of a Terrier sitting on a rock

Osteosarcoma is one of the most common malignant types of bone cancers that affect dogs. It is similar, to some extent, to pediatric osteosarcoma, which happens in humans in adolescence when teenagers experience a period of rapid growth. Typically, osteosarcoma affects larger breeds and older dogs, but there are many cases where dogs are diagnosed and they are only 1 or 2 years old.

Let’s look at the symptoms of osteosarcoma in dogs, how the disease is diagnosed, and how it can be treated.

Causes

As is the case with many other types of cancer, the causes of osteosarcoma are idiopathic, so they can be represented by a collection of factors or none of them. There are oncogenic viruses, but there’s also the genetic factor that should be taken into account. If you know that one of your dog’s parents had osteosarcoma, it’s safe to say that you should be prepared to manage it if it ever affects your dog.

It is more common in larger breeds simply because, in them, there is more pressure and force placed on the bones. Osteosarcoma can also appear near fracture sites that were repaired with the use of plates or metal pins being inserted into the bone. Furthermore, any body areas that were exposed to radiation are more vulnerable and could develop osteosarcoma.

Clinical signs

Osteosarcoma is typically present in one of the limbs, so one of the symptoms that can be noticed by the pet parent consists of lameness without any noticeable swelling or mass at the tumor site.

However, the swelling can also appear, and it is caused by the extension of the tumor into the soft tissues that surround the bone. The cancer might not spread to the muscle, joints, or ligaments – but as it grows in size, it puts so much pressure on them that it causes inflammation. Usually, this happens in later stages of the disease.

Lameness is typical for the initial stages where only the bone and its surface are affected, in which case the dog will avoid using that limb.

Osteosarcoma can also show up in body locations such as the mandible, the skull, and the pelvis. Naturally, the symptoms of each are different. Dogs with mandibular cancer will have difficulty swallowing, those with vertebral or cranial tumors will have neurologic deficits while those that have pelvic masses could experience difficulty defecating (at first).

Other signs that pet parents could notice range from intolerance to exercise to labored breathing, pain in bones, fractures as a result of very mild or mild trauma, and coughing.

Diagnosis

X-rays and histopathology can be essential when it comes to discovering whether a dog is indeed suffering from bone cancer or not. Even though the risk of fracture is low when performing a biopsy with an 18-gauge hypodermic needle, it can happen, so the pet owner must also take that into account.

The degree to which the primary tumor has metastasized must also be established, and that is why dogs that have tumors in their limbs might have to be performed X-rays of the chest, for example. Metastatic osteosarcoma has a bad habit of spreading to the lungs and other organs.

Almost 90% of the cases of bone cancer that are diagnosed will have metastasized, and that is why the treatment is often performed as if the dog already had metastases.

Treatment of Osteosarcoma

Given that it is a highly metastatic cancer, osteosarcoma is quite likely to spread to other organs. This means that the prognosis is considerably poorer than that of other cancer cases. Combination therapy is available, and it usually consists of the amputation of the affected limb followed by chemotherapy for dogs with osteosarcoma.

While it is used somewhat less frequently, radiation therapy can also offer good results at least in terms of alleviating part of the pain.

Because it is a painful type of cancer, osteosarcoma often calls for pain medication, as well. In such situations, your vet will likely prescribe NSAIDs as well as other anti-inflammatory drugs. More powerful meds might be required when the dog is in severe pain, but we have to underline that this type of cancer cannot be treated only with anti-inflammatory medication and that surgery and chemotherapy have no replacement.

Osteosarcoma – Dog life expectancy

How long can a dog live with osteosarcoma? Both the extent of the metastasis, as well as the severity of the medical condition, have to be taken into account when deciding on a prognosis. In most cases, it is poor.

The average life expectancy of dogs that have appendicular osteosarcoma and that do not receive treatment is somewhere around two to four months. A dog whose leg was amputated and has received chemotherapy is expected to live for twelve more months.

The prognosis is much poorer if the cancer has metastasized to the chest. Although the total percentage is smaller, some research studies have shown that dogs that were treated with surgery, chemotherapy, and radiation therapy and that weren’t suffering from aggressive types of osteosarcoma were able to survive for as many as two years following the diagnosis.

Most dogs that have cancer in their lower jaws and that have been operated can live for one more year without any other type of treatment.

What dogs are more likely to get osteosarcoma?

Large breeds are more predisposed to this type of cancer. Some studies suggest that one out of every eight Rottweilers will develop osteosarcoma.

Other large breeds such as Dobermans, German Shepherds, Golden Retrievers, Boxers, as well as Labradors are at greater risk, and gigantic breeds such as Great Danes, Newfoundlands, or Saint Bernards are even more predisposed to getting bone cancer.

Final thoughts

Compared to other types of cancer, osteosarcoma is far more difficult to manage, and the diagnosis can be heartbreaking. Pet parents are often confronted with two choices – treat their dogs and expect them to live only for a short amount of time or choose to put them down to end their pain.

Many dogs that are diagnosed with this unforgiving medical condition don’t care for much activity, can’t get out of bed, and won’t care for food, either. Osteosarcoma can significantly affect their quality of life, and that’s why many dog owners will choose euthanasia, no matter how difficult or emotional it might be.

For cases where dogs are euthanized later, CBD oil and anti-inflammatory meds can at least make the pain bearable.

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