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Osteosarcoma: Bone Cancer in Dogs

Reviewed by Dr. Peter Kintzer, DVM, DACVIM on Thursday, May 21, 2015
Posted May 21, 2015 in Dog Diseases & Conditions A-Z

German short-haired pointer laying down outside

One of the most disheartening diagnoses I encounter is osteosarcoma. It’s a painful and aggressive form of bone cancer that has an affinity for growing within the leg bones of large and giant-breed dogs. Less commonly, osteosarcoma occurs within the bones of the skull or spine. Although older dogs are primarily affected, dogs of all ages can develop osteosarcoma.

While I have the ability to improve my patient’s quality of life for a period of time, with rare exception, a cure for this disease will not be possible. By the time the dog begins favoring the painful leg, microscopic cancer cells will have already spread, typically to the lungs or other bony sites. Sooner or later these tiny clusters of cells will grow into metastatic tumors that will ultimately become life ending.

Symptoms of bone cancer
The most common symptom associated with osteosarcoma is lameness. Lameness caused by osteosarcoma is typically mild at the onset, but then progresses over time. The level of pain can morph quickly from mild to severe if the diseased bone suddenly develops a crack (microfracture) or a full, bony break.

Diagnosis of bone cancer
The diagnosis of osteosarcoma is suspected based on characteristic changes seen on x-rays or a computed tomography scan (CT) of the affected body part. A definitive diagnosis is made based on bone biopsy results.

Treatment options for bone cancer
Once the diagnosis of osteosarcoma has been made, there’s a great deal to be gained from consulting with a veterinarian who specializes in oncology to discuss the overall treatment plan. If surgery is part of your dog’s therapy, you may be referred to a surgical specialist. Surgery is the key component treatment for osteosarcoma. Treatment options for bone cancer include the following:

Surgical amputation
The most commonly recommended treatment for osteosarcoma is amputation (surgical removal) of the affected limb. For the uninitiated, amputation may seem like an overwhelmingly radical next step. However, those experienced with three-legged dogs know that most of them adapt quickly and amazingly well, both physically and emotionally, to their newfound tripod status. The caveat here is that in order for amputation to be successful, the dog’s other three limbs must be strong, sturdy and free of disease such as significant arthritis.

  • Why perform such an aggressive surgery, when the result will not be curative? The answer is simple. Osteosarcoma is a dreadfully painful disease. A primary goal of therapy is elimination of that pain with restoration of a good quality of life. Amputation has the ability to accomplish both of these objectives.
  • Is amputation the right choice for every patient with osteosarcoma? No way! The elderly German Shepherd who has been a couch potato, because of severe arthritis in multiple joints, is very unlikely to adapt well to life as a three-legged dog. Conversely, the older German Shorthaired Pointer who has been a lean, mean, running machine will very likely be back to all of his usual tricks within a couple of weeks following surgery.

If ever you must consider amputation for your dog, it is imperative that together, you and your veterinarian do some significant soul searching to determine if this surgery makes good sense.

Limb-sparing procedure
Another surgical option for the treatment of osteosarcoma is referred to as limb sparing. This involves removal of the portion of the bone that contains the tumor, without removal of the entire limb. Not all dogs are appropriate candidates for this surgery, as the tumor must be located in just the right spot within the bone. Compared to amputation, limb-sparing surgery is technically more difficult, significantly more expensive and requires a longer period of recovery and confinement. Limb-sparing surgery is certainly worthy of discussion as an alternative to amputation.

Chemotherapy
Chemotherapy (the administration of cancer fighting drugs) is recommended as treatment, only following surgery. It can stave off the growth of the microscopic metastasis, those cancer cells that have already managed to spread by the time of diagnosis. As a “stand alone” treatment (administered without surgery), chemotherapy is woefully ineffective at battling the primary cancerous growth.

The chemotherapy drugs most commonly used to treat osteosarcoma following surgery are carboplatin and doxorubicin. Average survival time following the administration of either drug is approximately 290 days, according to a journal of veterinary internal medicine article.  For surgery alone (no chemotherapy), the average survival time is approximately six months.

Dogs tend to tolerate chemotherapy far better than we do. Rarely do they experience significant hair loss, vomiting or loss of appetite.

Other treatment options for bone cancer
When surgery is not an option, other therapies may effectively reduce the pain associated with osteosarcoma. A few treatments of radiation therapy can do wonders and nonsteroidal anti-inflammatory medications, narcotics and a class of drugs called biphosphanates are all reasonable options for mitigating discomfort and enhancing quality of life.

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Nancy has more than 30 years of experience in the veterinary industry and is a board-certified veterinary specialist in internal medicine as well as a valued member of IDEXX’s Pet Health Network team since 2014.