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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. Heidi Mcknight on May 11, 2018 at 9:31 am

    my dog has bone cancer i am treating him holisticlly no more kibble homemade meals only essential oils turmeric mushrooms herbs for liver cbd oil essiac tyea
    and arteminisis the tumor on his leg has grown 4 inches in a month in a half why is nothing helping

    • DogCancerBlog on May 14, 2018 at 11:31 am

      Hi Heidi, thanks for writing, and we’re sorry to hear about your pup. It sounds like you are really doing everything you can think of, and hopefully, you have a veterinarian supervising all of that. The sad fact is that osteosarcoma is an aggressive cancer, as you are noticing. This is one of the reasons so many people end up choosing to amputate the limb — even if it doesn’t result in a “cure” it does increase quality of life and reduce the pain for the dog. You might benefit from reading the forums at if you haven’t already found them. Very helpful!

  2. Lynn Elwell on April 8, 2017 at 4:45 pm

    PS – I also switched Maya to raw food when I found out about her diagnosis….not for any other reason than to give her the best possible food while she was palliative.

  3. Lynn Elwell on April 8, 2017 at 4:42 pm

    My best friend Maya (almost 9 year old 75 pound Bouvier) was diagnosed with advanced osteosarcoma on Jan. 7/17. Maya was an amazing friend to me and I’m so sad that she’s gone..cancer sucks and she didn’t deserve to get it. My reason for posting is that I was only able to offer her palliative care because the cancer was so advanced. My vet determined that she wasn’t a candidate for amputation because of her double TTA surgeries on her back legs and only one good leg in the front. I could talk a lot about our last two months together, but mainly, I would like to share that when your best doggy friend has osteosarcoma in the wrist and can’t be treated, you are simply making her life as happy as possible until she is in too much pain, or has fractures from normal activities. Maya was on mushroom supplements to help stop the cancer progression. She also was on Meloxicam for pain and inflammation as well as 20 mg X 2/day of CBD oil from cannabis. I believe the CBD oil helped her pain as well as her outlook. She was still very puppylike until the day before she was euthanized, which happened very peacefully in her favourite corner of our backyard. Unfortunately about a week before, she had fractured the bones in her wrist and her leg from the wrist to the tips of her paw had swelled up a lot and was obviously infected. She still moved on three legs to go out for potty breaks and the day before, we even went for a really short “walk” with her going really fast on three legs. Her best friend (human and doggy) visited on that day and we all howled together, gave her lots of treats and she still tried to get up and play with us. Although I can’t say that CBD oil (from cannabis, not hemp) was the reason for how well her pain was managed, I would like to say that she didn’t have any signs of aggression, lack of appetite, inability to go outside for potty breaks and still wagged her tail when she was happy, until the end.

  4. Lori Barrett on June 16, 2015 at 6:54 pm

    I just found out my 10yr old dog Midnight has osteosarcoma. She also has an old injury which is torn acl from when she was 4 yrs old that never got fixed. She has lived with that really well. But I would like advice if amputation would be a good option especially with a bum back leg and the weight bearing issue

    • Susan Kazara Harper on June 16, 2015 at 7:10 pm

      Hi Lori,
      So sorry to hear about the diagnosis. Give mIdnight a big cuddle from all of us, and one for you. The decisions about amputation surgery is hard, as all of these decisions are in a cancer journey. You are right that weight and the condition of the other legs both play a big part in making this decision. Whether the surgery is right for Midnight is really down to you with the advice from your vet. If the osteosarcoma is localised and hasn’t metastacized, it also plays a part. Dr Dressler and Dr Ettinger devoted and entire chapter (chapter 12) to osteosarcoma in their book The Dog Cancer Survival Guide. It really goes into all the considerations, options for treatment etc. that would be very hard to cover here. Nutrition will play a huge part in Midnight’s ability to respond to whatever options you choose and of course the chapter in the Dog Cancer Diet gets into the food to feed, and those to avoid, during a cancer fight. There is also a terrific website, which is devoted to all the options of a three legged lifestyle. I have seen many dogs bound around three days after surgery; it’s not as debilitating for them as we humans believe. But just like us, each dog is an individual. I urge you to check the resources I’ve mentioned, read that chapter so you have some good information to work with your vet, and talk with Midnight. When you know what is in her heart and what her wishes are, combined with the medical information, you will be able to make a decision that you will feel content with. Good luck to you both. There is so much you can do, and the biggest first step is to get informed as you take the panic away from your heart. Hold that girl close and she’ll know you’re in this together.

  5. mary on April 6, 2014 at 2:22 pm

    I have a very large labradoodle (weighs over 100lbs), he will be 9 in two months. My dog has an extremely high pain threshold, and he never shows pain until its almost too late. I work at a vet clinic and I brought him in for limping, we thought was from potentially injuring himself the previous day. My doctors couldn’t feel anything nor did he show any discomfort or pain aside from limping. After taking x-rays, I was told that it looks just like osteosarcoma but that he was not reacting painfully to them pressing/touching his leg like they would normally see in cases of bone cancer. We decided to send the views out to get further answers because they weren’t sure what to make of it since the only pain my dog has been showing is by limping. The past few weeks my dog has been really lethargic and has not been wanting to eat very much and I thought he was just showing signs of old age until I read about cancer signs/symptoms in dogs. The results from our outside radiologist will not be in for another day or two, and I am just wondering could it be possible that my dog has osteosarcoma even if he doesn’t show that he is in extreme pain?? Any opinion would be helpful

    • Susan Kazara Harper on April 7, 2014 at 2:30 am

      Hello Mary, Every dog is different, just as every human is, so yes, it could be osteosarcoma. But before you put too much energy into worry, get those results back. You’re fortunate to have access to diagnostics and I’m glad you got him checked immediately. The thing with osteosarcoma, sometimes the discomfort may only be shown when weight is put on the leg, rather than on palpating or pressing the area. If he’s been off his food and lethargic lately, something is bothering him. Here’s another link that might help you: If it is a confirmed diagnosis for your boy, there is a lot you can do, so please stay positive. If your vet has an oncologist to refer with, that will really help. Nutrition is also key (at any stage, of course but particularly if he’s got a chronic situation to deal with) so you may want to download the Dog Cancer Diet at the top of the blog page. The full diet plus loads of other information is in the Dog Cancer Survival Guide book. Good luck. Give him a big cuddle from us. Let us know if we can help in any way going forward. We’re with you.

  6. Mike on September 14, 2013 at 10:45 am

    My greatdane girl, Angel was diagnosed with Osteosarcoma 4 years ago and an amazing vet at Mililani Mauka Vetinary Clinic did surgery and chemo. Prognosis had been poor but this tx gave her 4 years. No other vet was willing to do this and I am not sure why. Anyways recently it has come back and is sprerading quickly. She looks miserable and I am giving her Tramadol. She is going to the vets today. My greatest concern is pain. She is almost 9 years old. I do not want her to suffer. I want to know if chemo or radiation would be advised. I also want a good pain management plan. I think paliative or Hospice for dogs would be compassionate for dogs and owners alike. I have had other dogs die from Cancer and basically there was no good pain management available. Vets always prescribed anti inflamatories which were useless. Help.

    • DrSueCancerVet on September 29, 2013 at 4:02 pm

      I am sorry about Angel. If the cancer is spread, you could consider oral chemo like Palladia or low dose oral/metronomic chemo. Radiation is a good palliative option for one are like a met/spread to another bone, but not the lungs. As for pain, there are lots of good options and often dogs need more than one from different categories – such as an NSAID, Tramadol, gabapentin, amantadine, fentabyl skin patches. And what works for one dog may not work for another, so work closely with your vet to find a safe combo for pain meds.
      All my best, Dr Sue

  7. Jolli on June 4, 2013 at 8:35 pm

    My Pyr was diagnosed w/OSA one week ago. He is 120# good health male 6 yrs old. Left rear leg affected, lungs appear clean. My question is how do these large breeds recuperate after amputation and get around? They are so big and mine can be tempermental at times when made to something he doesn’t want to do. I need to make a decision quick. Amputation vs pain, amputation and chemo, or let it be and use pain meds. Anyone with a large Pyr??

    • Susan Harper on June 6, 2013 at 9:40 pm

      Hello Jolli, I’m sorry to hear that you are battling a cancer diagnosis with your wonderful dog. You are good to consider all the possible options to both help him and give him the best quality of life. It is understandable to resist the recommendation for amputation… to our human minds it is an incredibly drastic option. But here are some thing to consider: Statistically, if you have a confirmed diagnosis of osteosarcoma, amputation of the affected limb is one of the best options you have, because you stand a good chance of literally cutting the cancer out of the body if it has not spread. The keys to knowing whether your large breed will cope is… (a) when a dog is in pain he begins to limp and not use the affected leg. In effect he is already rehabilitating himself to rely on the other three legs. Remember they have four altogether, and we only have two, so it’s harder for us to adjust to losing half of our resources! (b) Your vet will want to really examine his other joints, particularly the other, healthy leg and hip to determine whether everything is sound and his joints and body can carry the adjusted weight well. There is a wonderful resource, which will give you more information and examples of dog who cope very, very well after losing one leg. If your vet specialist recommends chemo after amputation, discuss it with him or her so you know what to expect. Dog can also cope very well with most chemo protocols. There is an extensive section in The Dog Cancer Survival Guide book which discusses osteosarcoma and most of the chemo protocols. I hope you have the book, and do you have your dog on the Dog Cancer Diet? Good nutrition is vital in this fight. IF you haven’t changed his diet, you can get all the info again from the book, and the main point of the diet are at Also, Apocaps can help in so many ways to support your dog in this fight. If you have not started with any of these portions of his care, please go to Dog Cancer Kit. Regarding your dog’s temperament, talk to him Jolli. Explain what’s going on, with your thoughts and fears, and with your love. He needs you as a champion now, and I can tell that you are have already taken on that role. Remember that if he is in discomfort with that leg, he will be irritable. I hope this helps. Please let us know how you get on. Susan from the Dog Cancer Support Team

  8. Tammy von Langen on February 23, 2013 at 5:18 pm

    My dog (lab mix) age approximately 11 was diagnosed today with bone-cancer. I have been trying to study my options and I understand amputation is best but he already has severe arthritis in his hips (recently had the stem cell procedure to help his arthritis) so I am concerned his arthritic remaining hip would not be strong enough. What are my options? Will radiation help the pain if I don’t amputate? He has an appointment with an oncologist on Tuesday but I am trying to learn everything I can in advance. Thank you.

  9. Karen on February 12, 2013 at 9:20 am

    My golden retriever had her front leg amputated 17 feb 2011 due to bone cancer but she sadly died 6 days later , the results from her lymph nodes showed that her cancer had spread every where

    • Dr. Susan Ettinger on February 24, 2013 at 9:02 am

      I am so sorry for your loss. Years after losing my Paige, I still miss her. I know the pain can be overwhelming.
      With sympathy, Dr Sue

  10. Steph on February 8, 2013 at 3:54 pm

    My 6 year old rottie passed at the end of October from Osteosarcoma. We did the amputation but within 3 months she had 2 huge masses in her lungs. I was working with a holistic vet and she was on the cancer diet as described in the book. She had trouble recouperating after the amputation and I decided against the chemo. (I was also dealing with my ailing mother at the time. She passed in September.) Towards the end her remaining legs swelled. The vet said her body was putting down new bone over her leg bones, something they see sometimes with osteosarcoma. She was a stray, I adopted her when she was 3 (we’re guessing). She had just been spayed and tested positive for heartworms when I adopted her. She went through the heartworm treatment. I can’t help but think that her life before I found her could have had an effect. What kind of nutrition did she get as a pup? What kind of stressors was she subjected to? I think the micro-fractures theory is interesting.

    I also find it interesting that Greyhounds in England rarely get osteosarcoma. I wonder if it’s food/nutrition related. There is so much garbage on the market in the US (just like US human food).

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