Canine Osteosarcoma, Our Experience Part I
Since Maggie was diagnosed with osteosarcoma (OSA) last month, I’ve done as much reading as I could about the disease. Having had two female black labs who both developed it, I also wondered about breed propensity for OSA. And finally, I looked at treatments recommended – particularly the Stereotactic RadioSurgery we are doing with Maggie. Needless to say, I have a lot to write, so this will likely turn into multiple posts.
Note: Our intent is only to inform and share our experiences. We are NOT veterinarians and nothing we say should be taken as veterinary advice. If you have any concerns about your own dog, see your vet.
Our first indication that something was wrong with Maggie manifested itself the same way it did with Becca…a simple limp in the affected limb. Both Becca and Maggie developed OSA in the left front limb – Becca in the shoulder and Maggie in the foreleg. Becca had many orthopedic problems, so I didn’t do much at first other than increase her normal dose of painkillers and rested her. When it didn’t improve we went off to the vet. The vet was able to discern fairly easily from Becca’s xrays alone that it was OSA as there is a fairly characteristic pattern which we will talk about.
With Maggie, we knew she had arthritis in her front legs, so we did the same at first, increased her arthritis medication, added a few pain killers and rested her. When she didn’t improve after a several days of rest, we went to the vet. After a few more agonizing days of waiting for a definitive diagnosis, we were finally told it was OSA. I’ll talk more about diagnostic methods in our next post.
From this point, the treatment for our two girls diverged. We will discuss treatment plans, but first let’s take a deeper look at OSA, what it is, what may cause it and how it affects our dogs.
Osteosarcoma is cancer of the bone. It is the most common bone tumor present in dogs, accounting for 85% of all malignancies in the skeletal system. This cancer normally affects the dog’s limbs. The tumor originates within the bone and destroys it from the inside out.1. OSA is highly aggressive and in 90% of cases has micro-metastasized to other parts of the body before it is even diagnosed.2. OSA metastasis is termed hematogenous, or carried through the blood to the lungs, other bones and possibly the thyroid. Long term prognosis is poor.
OSA develops deep in the bone and creates a great deal of pain as the tumor grows outwardly, destroying the bone as the tumor grows. The bone is weakened as healthy bone is replaced by the tumor, so an immediate concern is a pathogenic fracture of the affected limb. A fracture of this type will not heal, so care must be taken for your dog’s safety during this time.
Our Becca used to love jumping off the landing from the kitchen into the family room – only two steps, but I was so afraid she would hurt herself, we built a ramp. Maggie loves to jump out of the back of our station wagon – onto the concrete driveway. I’m struggling with getting her to use the steps we’ve gotten. She’s good about going up the steps, but not so good about coming down.
While there is no specific research to support a genetic link by breed, Rottweilers are by far the breed most susceptible. It occurs most frequently in large breed dogs, with dogs over 80 pounds sixty times more likely to develop OSA than dogs weighing under 75lbs.3. It occurs more frequently in males than females. It has also been noted that it occurs most frequently near growth plates and there is some speculation that diets which encourage rapid growth in puppies may be a risk factor.4.
There have been studies examining early spay/neutering as a factor. In a study of Rottweilers, it was shown that male and female Rottweilers with the shortest lifetime gonadal exposure had the highest risk for bone sarcoma.5. In addition, dogs with OSA have been found to have aberrations of the p53 tumor suppressor gene (whatever that is). Other risk factors include exposure to ionizing radiation, chemical carcinogens, foreign bodies, (such as bullets or bone transplants), and pre-existing fractures or other skeletal problems. 6.
I have no idea how or why either of our girls developed OSA. Since both of them came to us late in their lives, I don’t know of any prior exposure to these risk factors – other than being large breeds. At this point, the “why” doesn’t really matter, what matters is what are we going to do about it. Next up: Diagnostic methods and treatment options.
1. Osteosarcoma | AKC Canine Health Foundation
2. Osteosarcoma (bone cancer)
3. Osteosarcoma in Dogs
4. Osteosarcoma (bone cancer)
5. Endogenous Gonadal Hormone Exposure and Bone Sarcoma Risk