Osteosarcoma in dogs is a common cancer overall and the most common type of bone cancer that affects our canine friends. No pet owner wants to think about cancer affecting their pet, but understanding the signs and risk factors can mean that cancer is diagnosed earlier so you can make informed decisions about your dog’s care.
Here’s what you need to know about osteosarcoma in dogs, including which dogs may be at risk, what to look for that might indicate your dog has osteosarcoma, treatment options for your pup, and the long-term outlook.
What is osteosarcoma in dogs?
Osteosarcoma (OSA) is an aggressive bone cancer that happens when osteoblasts, the bone cells responsible for creating new bone, grow out of control and form a malignant tumor. As the tumor grows, it destroys and weakens healthy bone. This causes pain and can leave the bone vulnerable to fractures from minimal impact.
Veterinarians classify osteosarcoma into three main forms.
Appendicular osteosarcoma
Appendicular osteosarcoma develops in the long bones of the legs. It most often occurs in the distal radius (near the wrist), proximal humerus (near the shoulder), and distal femur or proximal tibia (just above and below the knee).
Axial osteosarcoma
Axial osteosarcoma affects bones of the skull, spine, ribs, or pelvis. This form is less common than appendicular osteosarcoma and can affect dogs of any size.
Extraskeletal osteosarcoma
Rarely, dogs can develop osteosarcoma in soft tissues rather than in bones.
What causes osteosarcoma in dogs?
Researchers haven’t found a single cause of cancer in dogs—it’s usually multifactorial. Any dog can develop osteosarcoma, but several factors may increase the risk for individual pets:
- Breed and genetics: Giant breed dogs and large breed dogs, including Great Danes, Rottweilers, Irish wolfhounds, greyhounds, and golden retrievers, are at higher risk, though any breed can develop cancer.
- Age: Osteosarcoma most commonly affects middle-aged to older dogs, with a median age of diagnosis around 7 to 10 years. However, this cancer can affect young adult dogs, too.
- Previous injury, surgery, or bone disease: Dogs who have broken a bone, have a metal bone implant, or have had a past bone infection (osteomyelitis) may be at higher risk of developing a bone tumor at that location.
Having risk factors doesn’t mean your dog will develop the disease. But if your dog is high-risk, you should schedule routine veterinary exams and monitor for signs of the disease at home.
Signs of osteosarcoma in dogs
The signs of osteosarcoma in dogs vary depending on the tumor’s location. However, many of the signs overlap with those of other conditions. If your dog shows any of the following, schedule a visit with your veterinarian to determine the cause:
- Lameness or limping: Limping on an affected leg can develop and quickly worsen with time.
- Swelling: Osteosarcoma lesions appear as firm, localized swellings near or on bones.
- Pain or sensitivity: Osteosarcoma is painful, so affected dogs may flinch, cry out, or even try to bite when touched near the tumor.
- Loss of appetite: Dogs who are dealing with pain or not feeling well may eat less than usual or skip meals.
- Lethargy: Affected dogs may refuse to go for walks, play, or use the stairs because of pain, or they may lie around more than usual.
- Muscle loss: Muscle wasting in the affected limb can develop when dogs stop using the leg or area due to discomfort.
- Difficulty eating: Dogs with osteosarcoma of the jaw or skull may struggle to chew or fully open their mouths.
How do veterinarians diagnose osteosarcoma in dogs?
If your veterinarian suspects osteosarcoma, they’ll use several tools to confirm the diagnosis and determine how far the disease has progressed.
- Physical examination and history: Your veterinarian will examine the area of concern, check for pain, and review your dog’s history.
- Diagnostic imaging: Osteosarcoma has a characteristic appearance on radiographs (X-rays). Your vet may also recommend advanced imaging, such as CT or MRI, to get a more detailed look at the tumor.
- Biopsy: To confirm the diagnosis, your veterinarian may collect a sample from the bone lesion using a fine needle aspirate or bone biopsy. A biopsy is the only way to definitively confirm osteosarcoma.
- Staging tests: Chest X-rays, abdominal ultrasound, and routine lab tests help determine the extent of disease. Unfortunately, many cases of osteosarcoma have already spread to other areas of the body by the time of diagnosis.
Treatment options and supportive care for osteosarcoma in dogs
Treatment for osteosarcoma in dogs depends on the tumor’s location, whether imaging tests show that cancer has spread, and your dog’s overall health. Your veterinarian may refer you to a veterinary oncologist for specialized care and to explore all treatment options.
Only a veterinarian can provide a proper diagnosis and recommend the best treatment plan for your individual dog. Common approaches include:
- Pain management: Medications, such as non-steroidal anti-inflammatory drugs (NSAIDs), gabapentin, or opioids, can help keep your dog comfortable.
- Limb amputation: When osteosarcoma affects a limb, amputation removes the tumor, relieves pain, and eliminates the risk of pathological fractures.
- Chemotherapy: Chemotherapy used after surgery can help to prevent or slow the spread of the cancer. Dogs tolerate chemotherapy well, with fewer than 5% experiencing serious side effects.
- Radiation therapy: Radiation therapy can help reduce pain in dogs who aren’t good candidates for surgery.
- Limb-sparing surgery: For select dogs, a veterinary oncologist may recommend a limb-sparing procedure instead of amputation.
- Bisphosphonate therapy: Bisphosphonates are medications that may help slow bone destruction and provide comfort.
- Supportive care: Continued veterinary care, nutrient-dense food, targeted supplements, and other veterinary-recommended interventions help maintain overall well-being during cancer treatment.
There is currently no definitive cure for osteosarcoma, and most pets pass away or are euthanized because of the disease. Treatment goals include managing pain, maintaining a good quality of life, and slowing progression.
Prognosis varies from dog to dog, but your veterinary care team will work with you to create a plan that reflects your dog’s needs and your family’s goals.
Supporting your dog during osteosarcoma treatment
If your dog has osteosarcoma, you can help them by working closely with your pet’s veterinary team to select and adjust treatments, and by providing a comfortable home environment with cozy bedding, mobility assistance, and quality nutrition. Spending quality time with your pet is also important.
JustFoodForDogs offers fresh, palatable diets designed to support dogs at all life stages. Ask your pet’s veterinary team which formula might be right for your dog.
Frequently asked questions about osteosarcoma in dogs
Is osteosarcoma in dogs painful?
Osteosarcoma is a painful cancer because it destroys and replaces healthy bone. Bone and its surrounding tissue, the periosteum, are highly sensitive structures—which is why it hurts so badly when you break a bone. Pain management is a key part of treatment for osteosarcoma in dogs.
Can osteosarcoma spread to other parts of the body?
Osteosarcoma is aggressive and typically metastasizes or spreads to the lungs or other parts of the body. Most dogs have microscopic spread at the time of diagnosis, even if imaging tests don’t show obvious tumors. Veterinarians treating osteosarcoma usually assume the disease has already spread when they design a treatment plan.
Can dogs live comfortably after amputation?
Most dogs adjust well to life on three legs and can return to normal activities, including walking and playing, within a few weeks of surgery. Amputation provides significant pain relief by removing the tumor and the affected bone. The median survival time after amputation combined with chemotherapy is approximately nine to 12 months.
