Osteosarcoma is the most common bone cancer in dogs, with more than 10,000 cases diagnosed in the United States every year. While that number sounds high, it overwhelmingly affects certain breeds and body types, meaning the actual risk for any individual dog depends heavily on size, genetics, and age.
Overall Incidence and Who It Affects
Osteosarcoma accounts for the vast majority of bone tumors in dogs. It follows a bimodal age pattern, meaning it clusters around two age groups. The larger peak hits older adults: 80% of cases occur in dogs over 7 years old, and more than half occur in dogs over 9. A smaller spike, representing roughly 6 to 8% of cases, shows up in dogs under 3 years old.
This isn’t a cancer that strikes randomly across the dog population. Body size is the single biggest predictor. Giant and large breeds carry dramatically higher risk than medium or small dogs, and the reasons are largely genetic. The same genes that control a breed’s large frame size appear to be linked to osteosarcoma susceptibility.
Breeds at Highest and Lowest Risk
A large study from the Royal Veterinary College put hard numbers on breed-specific risk, and the differences are staggering. Scottish Deerhounds are 118 times more likely to develop osteosarcoma than crossbreed dogs, with 3.28% of all Deerhounds affected each year. Leonbergers are 56 times more likely (1.48% per year), Great Danes 34 times more likely (0.87% per year), and Rottweilers 27 times more likely (0.84% per year).
On the other end of the spectrum, several breeds have significantly lower risk than even average crossbreeds. English Cocker Spaniels have about one-fifth the risk of crossbreeds. Shih Tzus have roughly one-eighth the risk, and Jack Russell Terriers sit at just one-twentieth the risk of a typical mixed-breed dog.
Two physical traits beyond sheer size also matter. Dogs with long, narrow skulls (think Greyhounds, Collies) have about 2.7 times the risk of breeds with medium-length faces. Flat-faced breeds have about half the risk. And breeds with the genetic mutation for shortened legs, like Dachshunds and Corgis, have only one-tenth the osteosarcoma risk of longer-legged breeds like Labrador Retrievers or German Shepherds. All of this points to a cancer deeply tied to skeletal genetics rather than environmental exposure.
Where It Develops in the Body
Unlike many other species where osteosarcoma tends to form in the spine, skull, or ribs, dogs get it primarily in their legs. Appendicular (limb) osteosarcoma accounts for 69 to 86% of all cases. The front legs are affected more often than the hind legs, particularly around the shoulder and wrist areas. When it does occur in the axial skeleton (the skull, jaw, ribs, or spine), it tends to behave somewhat differently, but these cases are the minority.
Signs to Watch For
The first thing most owners notice is lameness, often in one leg, that doesn’t improve with rest. It can look like a sprain or arthritis at first. Over days to weeks, the lameness typically worsens, and you may notice swelling at the affected site. The area around the tumor can become firm and painful to the touch. In some cases, the first sign is a sudden fracture from a bone weakened by the tumor, which can happen during normal activity like jumping off a couch or playing in the yard.
Because early lameness mimics so many other conditions, osteosarcoma is sometimes treated as a soft tissue injury before imaging reveals the real problem. If your dog is a large or giant breed over 7 years old and develops persistent, worsening leg pain, that combination warrants X-rays sooner rather than later.
How Aggressive It Is
Osteosarcoma is one of the more aggressive cancers in veterinary medicine. It tends to spread to the lungs early, often before the primary tumor is even diagnosed. By the time most dogs show symptoms, microscopic spread has typically already occurred, even if chest X-rays look clear.
Without chemotherapy, dogs treated with amputation alone have a median survival time of about four months. When surgery is combined with chemotherapy, that median extends to roughly nine months. About half of dogs treated with both surgery and chemotherapy are alive one year after diagnosis, and approximately 25% make it to two years. A small number of dogs are effectively cured, but they are the exception. Dogs treated only with pain management or palliative radiation typically live about six months before the disease progresses to the point where quality of life becomes untenable.
These numbers reflect averages. Individual dogs vary considerably in how they respond to treatment, and factors like the tumor’s location, how early it’s caught, and the dog’s overall health all influence the outcome.
Putting the Risk in Perspective
If you own a small or medium-sized breed, osteosarcoma is uncommon enough that it shouldn’t be a major worry. A Jack Russell Terrier’s lifetime risk is vanishingly small. But if you have a Scottish Deerhound, Great Dane, Rottweiler, or another giant breed, osteosarcoma is a realistic concern, especially once your dog passes age 7. For these breeds, it’s worth being aware of the early signs and not dismissing persistent limeness as “just getting old.” Early detection won’t change the biology of the cancer, but it gives you more options for managing it and maintaining your dog’s quality of life for as long as possible.