Posted on November 5, 2012
A Primer on Osteosarcoma
One of the most disheartening diagnoses I must deliver is that of osteosarcoma, a painful and aggressive form of bone cancer that has an affinity for growing within the leg bones of large and giant- breed dogs. I must explain to my client that, while I have the ability to improve upon their best buddy’s quality of life for a period of time, with rare exception, a cure 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.
The 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 on bony break.
The most commonly recommended treatment for osteoscarcoma is amputation (surgical removal) of the affected limb. For the uninitiated, amputation may seem like an overwhelmingly radical next step. 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 and sturdy and free of disease such as significant arthritis.
Perhaps you are wondering, why perform such an aggressive surgery, when the result will not be curative? The answer is simple. Osteosarcoma is a dreadfully painful disease. The 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 with 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 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. One of my favorite client support websites is Tripawds, a community of people who have “been there, done that” and can offer a whole lot of experiential wisdom pertaining to the decision of whether or not to proceed with limb amputation.
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- 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 (the administration of cancer fighting drugs) is recommended as a treatment only following surgery. Chemotherapy can stave off growth of the microscopic metastasis- those cancer cells that have already managed to spread by the time of diagnosis. As a “stand alone” therapy (administered without surgery), it is woefully ineffective at battling the primary cancerous growth. Approximately half of the dogs treated with surgery followed by chemotherapy will be alive one year following diagnosis; approximately 25% will be alive two years following diagnosis, and every once in a great while, a cure will be achieved. Compare this to surgery alone (no chemotherapy)- the average survival time is approximately six months.
The good news is that dogs tend to tolerate chemotherapy far better than we do. Rarely do they experience significant hair loss, and vomiting and loss of appetite tend to be the exception rather than the rule. If this were not the case, I’m doubtful that many veterinarians would be willing to administer chemotherapy drugs.
Other treatment options
When surgery is not an option, other therapies may effectively reduce the pain associated with osteosarcoma. A few treatments with radiation therapy can do wonders and nonsteroidal antiinflammatory medications, narcotics, and a class of drugs called biphosphanates are all reasonable options for mitigating discomfort and enhancing quality of life.
Research to develop an osteosarcoma vaccine is currently underway at the University of Pennsylvania School of Veterinary Medicine. The hope is that this vaccine will stimulate the immune system to hone in on cancer cells containing a specific genetic marker found in approximately 40 to 50 percent of dogs with osteosarcoma. I will keep you posted on any new developments. In the meantime, if your dog has been diagnosed with osteosarcoma and you happen to live near Philly, consider enrolling in this clinical trial.
Several dog breeds are highly predisposed to developing osteosarcoma. Breeders of Rottweilers, Irish Wolfhounds, Great Danes, Saint Bernards, Doberman Pinschers, Labrador Retrievers, Golden Retrievers, Greyhounds, Samoyeds, Akitas, and Siberian Huskies should pay close attention to osteosarcoma incidence within their lines with hopes of altering the inheritance pattern of this deadly disease.
Some fascinating research involving Rottweilers documented that individuals neutered before one year of age had significantly increased risk of developing osteosarcoma later in life. This information is truly compelling and gives rise to a number of other questions. Does this data apply to other breeds? Does the timing of neutering affect development of other types of cancer? When is the ideal time to neuter Rottweilers and other large and giant breeds? My hope is that future research will begin to answer some of these questions.
Have you ever cared for a dog with osteosarcoma? If so, what did you choose to do?
Nancy Kay, DVM
Diplomate, American College of Veterinary Internal Medicine
Author of Speaking for Spot: Be the Advocate Your Dog Needs to Live a Happy, Healthy, Longer Life
Author of Your Dog’s Best Health: A Dozen Reasonable Things to Expect From Your Vet
Recipient, Leo K. Bustad Companion Animal Veterinarian of the Year Award
Recipient, American Animal Hospital Association Animal Welfare and Humane Ethics Award
Recipient, Dog Writers Association of America Award for Best Blog
Recipient, Eukanuba Canine Health Award
Recipient, AKC Club Publication Excellence Award
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Please visit http://www.speakingforspot.com to read excerpts from Speaking for Spot and Your Dog’s Best Health. There you will also find “Advocacy Aids”- helpful health forms you can download and use for your own dog, and a collection of published articles on advocating for your pet’s health. Speaking for Spot and Your Dog’s Best Health are available at www.speakingforspot.com, Amazon.com, local bookstores, and your favorite online book seller.