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Featuring Demian Dressler, DVM and Sue Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

Osteosarcoma Part One

Updated: April 15th, 2019

Osteosarcoma (OSA) is the most common bone cancer in dogs, accounting for about 85% of bone cancer cases. The bottom line on OSA is that metastasis is a problem: 90% of patients will die from the metastasis within the 1st year when amputation is the only treatment. Those are grim statistics, but it is the bone pain from the tumor itself that creates the biggest challenge to most clients I meet. In an upcoming post I will focus on the decision to amputate and the myths I hear. But first, let’s get background info out of the way.

Which bones are most common to develop osteosarcoma?

Osteosarcoma can develop in any bone in the body, but three-quarters develop in the limbs, with the front legs twice as likely to develop osteosarcoma as the hind legs. OSA tumors are usually found at the end of the bone (called the metaphysis), and this can help to distinguish them from bone tumors that have spread from other primary cancers, which are usually found in the middle of the bone (called the diaphysis). The most common locations for OSA are the top of the shoulder (top of the humerus bone), the wrist (bottom of the radius bone), and the knee (bottom of the femur bone or the top of tibia bone). Another common site is the bottom of the tibia bone at the ankle or hock joint. OSA can sometimes be found in the middle of bones and in body bones, but this is less common.

Why is osteosarcoma considered to be aggressive?

Osteosarcoma (OSA) tumors grow fast and metastasize quickly. Only 10 to 15% of dogs with osteosarcoma already have detectable lung metastasis when they are first diagnosed, but a whopping 90% have micrometastasis (undetectable spread). This incredibly high rate of micrometastasis makes systemic chemotherapy treatments just as important as tumor removal. Treating the primary bone tumor does not address the metastasis. Still, despite this aggressive behavior locally in the bone and the metastasis, OSA is a highly treatable tumor, in my opinion.

Tumors can also metastasize to other bones, but this is less common. The regional lymph nodes can also be involved, although this only occurs in 5% of dogs.

Which dogs get osteosarcoma?

Limb osteosarcoma is usually seen in middle-aged and older dogs, age seven to nine, but we also see a smaller peak incidence in dogs between the age of eighteen months and two years. Axial OSA can be seen in any breed at any time, but limb OSA is usually seen in the front limbs of large and giant breeds, including Great Danes, Saint Bernards, Irish Setters, Rottweilers, German Shepherds, Golden Retrievers, and Doberman Pinschers. Breed is not as important as height and weight; heavier and taller dogs are more likely to develop OSA.

What causes osteosarcoma?

Many different factors have been found that may influence the incidence of this disease, although the exact cause of OSA is unknown. One theory is that small “micro-fractures” occur in the long bones as they bear the weight of the dog’s body. These tiny fractures and subsequent multiple minor injuries in cells can lead to signals that increases the chances of mutant cells and developing malignancies.

There is an also association with surgical metallic implants (like those used to repair a fracture), bone infection, bone trauma, and even fractures without internal fixation has also been found. Radiation exposure — previous radiation treatment that bone was included in the radiation field — can lead to OSA later in life.  This late complication of ionizing radiation is rare and  usually happens three to five years after radiation treatments for other cancers that a bone was included in the radiation field.

Sex hormones have recently been shown to protect against OSA development. The interesting study was of Rottweilers who were spayed or neutered before one year of age: they were four times more likely to develop OSA later in life.

A number of molecular and genetic factors have been implicated in OSA development. Some genes researched include mutated p53 (a tumor suppresser gene), retinoblastoma, PTEN, and possibly c-Kit alterations. Angiogenesis, new blood vessel formation, can also play a role in OSA development and progression. Other growth factors, cytokines, and hormone signaling systems, alterations in matrix metalloproteinases,

What are the symptoms of osteosarcoma?

OSA bone tumors can cause pain, lameness or limping, weakness and even severe bone fractures in the primary site. The risk of a pathological fracture, a sudden and painful bone break, is real, which is why amputation is the most prudent immediate course to take. We will talk about treatment including amputation more in a future blog.

As I said above, despite the aggressive behavior locally in the bone and the high metastastic rates, osteosarcoma is a highly treatable tumor in my opinion. Next, we will talk about getting a diagnosis and treatment.


Leave a Comment

  1. Judy on February 7, 2013 at 1:27 pm

    I just read an article in the Penn Veterinary “Penn Vet Extra” regarding a vaccine for osteosarcoma in dogs.

    Maybe some readers as well as Dr. Dressler and Dr. Susan Ettinger will find some helpful and interesting information.

    • Dr. Susan Ettinger on February 9, 2013 at 10:42 am

      Yes this is an exciting study. As the article points out, it is too early to know if the vaccine will increased survival, but it would be great to have more treatment options for OSA.
      Thanks for sharing with us and our readers.
      All my best, Dr Sue

  2. Debra on February 7, 2013 at 8:02 am

    My Louie a great Pyrenees is 6 months post amp. I take him to a holistic doctor and give him everything I can to boost his immune system. We opted to not do chemo. Chemo, in my opinion, wrecks an already weak immune system. We give him artemisinin as well as many other herbs. In my opinion much of the cancers our dogs are suffering from is caused by weakened immune systems because the dog food we feed them is full of awful stuff.

    • Dr. Susan Ettinger on February 9, 2013 at 10:33 am

      Chemo is not for every pet Guardian, but for OSA, chemo does statistically and significantly increase how dogs live after amputation. And I think chemo is tolerated very well by most dogs. Still each person must weigh the pros and cons and decide what is right for them. I am trying to help pet owners make educated decisions. Thanks for sharing and good health to Louie!
      All my best, Dr Sue

  3. Sandra Owens on February 7, 2013 at 5:54 am

    My racing greyhound died at 13 from bone cancer probably due to the stress on her bones on the racetract. She may have had small fractures that no one knew about and this could have attributed to this. I have another greyhound now who is 11 years old but nothing so far. Hope he does not get bone cancer due to him also being a race dog.

    • Dr. Susan Ettinger on February 8, 2013 at 6:55 pm

      Knowing you have a breed at risk, be vigilant with monitoring including watching for lameness, limping. While it could simply be arthritis, you can be proactive and get into your vet promptly.
      All my best, Dr Sue

  4. theresa on February 7, 2013 at 5:08 am

    I have heard of something called Hoxey Boneset that is often used as a treatment in osteosarcoma cases. What is it and has it been used with success?

    • Dr. Susan Ettinger on February 8, 2013 at 6:53 pm

      It’s a mixture of herbs created by an insurance salesman in the 1920s and promoted as a cure to cancer. It has not been shown to be effective. In the Guide, my co-author Dr D does not recommend it. I have never used it.
      All my best, Dr Sue

  5. Linda Vick on February 7, 2013 at 3:46 am

    Dr. Ettinger,
    Please do not leave Greyhounds out of the group of dogs that develop Osteosarcoma. Important research is being done by Dr. Guillermo Couto at Ohio State University that may someday lead to a cure not only for canines but for humans, too!
    I hope that your readers understand that “treatable” is not the same as curable. 5 years is the record survival time post diagnosis for a Greyhound in the US. Did you know that Osteosarcoma is unheard of in Greyhounds in England and Ireland?

    • Dr. Susan Ettinger on February 8, 2013 at 6:47 pm

      Hi Linda,
      You are the 2nd comment about Greyhounds. Yes they are a breed that we see too many OSA! And Dr Couto and his research at OSU is great.
      Your distinction of treatable vs curable is correct, but dogs with treatment live statistically longer (and with better quality to life) than without treatment. Still OSA is touch and more treatment options are needed!
      All my best, Dr Sue

  6. Jane on February 6, 2013 at 1:50 pm

    Thank you so much for this article. This hits very close to home with me.

    One fourth to one third of retired racing greyhounds in North America develop osteosarcoma. This is true whether or not they raced. Spanish greyhounds have a much smaller incidence of osteosarcoma, despite being a very similar breed and running for more hours than a racer. To me this would imply that, in the US stock of racing greyhounds at least, the problem is primarily genetic. Unfortunately, not being a doctor-type, I don’t totally understand the genetics you mention. I just appreciate all that the oncologists do to treat and hopefully reduce the incidence of this disease.

    You mentioned that a study in Rottweilers implicated that early spay/neuter might be involved. Since racing greyhounds are not spayed/neutered until they retire at about 3 to 5 years of age, would this seem to negate the Rottweiler study? Female greyhounds do receive hormones to keep them out of heat during their racing career, but males do not. Both get osteo. I guess I’m wondering what your take on this might be?

    Thankfully, due to their relatively light weight and narrow body, the greyhound responds extremely well to amputation. My greyhound, Joe, survived for 20 months after amputation of his right front leg. He had IV chemo followed by a metronomic protocol for his remaining life. Ultimately he developed a second primary tumor in his left rear leg and I had to let him go. He was my heart and soul. He couldn’t have been a better companion.

    • Dr. Susan Ettinger on February 8, 2013 at 6:41 pm

      Hi Jane,
      Great point about Greyhounds who are not spayed/early. This is a complicated cancer with many factors at play. I don’t want to imply that all dogs that get spayed/neutered get this cancer or that sex hormones are compositely protective.
      Sorry to hear about Joe. Years after the loss of my Paige, a huge hole remains in my heart.
      With sympathy, Dr Sue

  7. Juliette on February 6, 2013 at 8:42 am

    Dear Susan

    One of my rescue dogs (a medium-sized lurcher) was neutered by the shelter at 8 months old. Should I be asking my vet for testosterone replacement therapy? Is such a thing available? He is 3 years old now, seems in perfect health and I need to keep it that way! I would very much appreciate your advice.

    Best wishes,


    • Dr. Susan Ettinger on February 8, 2013 at 6:37 pm

      Spay and neuter does not mean your dog will get OSA. It’s one of many contributors. So focus on good diet, maybe a supplement like EverPup, and routine veterinary visits.
      All my best, Dr Sue

    • Dr. Susan Ettinger on February 8, 2013 at 6:37 pm

      Spay and neuter does not mean your dog will get OSA. It’s one of many contributors. So focus on good diet, maybe a supplement like EverPup, and routine veterinary visits.
      All my best, Dr Sue

  8. KP on February 6, 2013 at 6:33 am

    Thank you for this article. Thankfully, I have not yet had to deal with cancer in my dogs and hopefully I won’t in the future. However, do you suggest that dog owners be proactive and perhaps feed the Dog Cancer Diet to an otherwise healthy dog? It seems like diet and nutrition in people can assist in preventing illnesses, I assume that is also the same for pets.

  9. Shelley Wall on February 4, 2013 at 6:36 pm

    Please sign me up for your newsletter. My precious 5 yr old Boxer, Roxie, is now 3 weeks post amp for osteosarcoma. I want to do everything possible to keep her healthy.

  10. Kate obrien on February 1, 2013 at 12:11 pm

    Thanks for this article. This is the type of cancer our dog Becca developed. I just wrote about her on our blog this week in response to a post about can dogs be too old for cancer treatments.

    While I’d read up on this cancer when Becca was first diagnosed, I never saw causation info…I think the idea of micro fracture is interesting, particularly in Becca’s case as she carried a pack as a service dog for many, many years. I can attest to its aggressiveness.

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