What You Should Know about Osteosarcoma (Bone Cancer) in Dogs and Cats
A type of bone cancer called osteosarcoma (OSA) is the most common type of primary bone cancer in dogs, accounting for over 95% of all bone tumors. Other types of bone cancer are chondrosarcoma, fibrosarcoma, and hemangiosarcoma. “Primary” refers to cancer that starts in the bone versus spreading (metastasizing) into the bone from somewhere else.1
The cause of OSA in dogs and cats isn’t well understood. Certain dog breeds are more prone to developing it. Scottish Deerhounds are genetically predisposed to OSA, and it occurs frequently in other large-breed dogs, especially Rottweilers. Large or giant/tall dogs are also at greater risk, as are middle-aged to older dogs.
Osteosarcoma can occur in any bone in a pet’s body, but in dogs, most tumors appear in the front limbs near the shoulder, wrist, and knee. OSA is extremely aggressive, and it spreads quickly to other parts of the body, making early detection and treatment vital.
While OSA is also the most common type of bone tumor in cats, it’s relatively uncommon. In addition, OSA is much less aggressive in cats than in dogs.
Signs and Symptoms of OSA
The symptoms of OSA can be subtle, and they may include:
- Lameness that doesn’t go away and swelling of the affected bone; these are the most common symptoms when a tumor affects a limb
- Swelling or a mass; this is often the first sign of a tumor in the skull, jaw, or ribs
- Difficulty eating if a tumor affects the jaw
- Neurologic signs, such as seizures or a wobbly gait, with skull or spinal/vertebral tumors
- Breathing difficulties or lameness with rib tumors
- Loss of appetite and lethargy
How Osteosarcoma Is Diagnosed
To diagnose OSA, veterinarians typically follow these steps:
- First, your vet will take an X-ray and perform a physical and orthopedic examination to rule out other causes of lameness.
- To obtain a definitive diagnosis and determine the best treatment plan for your pet, any problem areas identified on the X-ray will be biopsied.
- Chest X-rays or a computed tomography (CT) scan, blood tests, and a urinalysis will be performed to assess your pet’s overall health and determine if the cancer has spread (in 90–95% of dogs, the tumor will have already metastasized at the time of diagnosis; OSA most commonly spreads to the lungs).2
Advanced CT imaging is often recommended for OSA tumors of the limbs because it provides better information for a veterinary surgeon to determine if surgery is possible and the extent of surgery necessary to achieve a favorable outcome.
Treatment Options for OSA
Because OSA tumors are so aggressive, amputating the affected limb followed by chemotherapy to treat metastasis is the most common treatment. While amputation isn’t the right option for all pets, otherwise healthy dogs can function quite well with three legs.
Limb-sparing surgery—in which the tumor is removed and the bone is replaced with another bone (either from your pet or from a bone bank)—may be an option depending on the tumor’s location and whether it is relatively small at the time of diagnosis. The complication rate for this type of surgery, particularly infection, is relatively high, however.
When surgery isn’t an option due to tumor location, stereotactic radiosurgery (SRS) can be beneficial. It can also be an alternative to amputation for dogs in which the OSA hasn’t destroyed a great deal of bone. This advanced, highly accurate type of radiation therapy focuses high doses of radiation to damage and kill OSA cells. Follow-up chemotherapy is still necessary.
Palliative treatment, which aims to make your pet more comfortable but doesn’t provide a cure, can include conventional radiation therapy and drugs to reduce pain.
The prognosis for pets with OSA depends on the severity and spread of the disease and on the treatment you choose.
Dogs with limb OSA that receive SRS and chemotherapy have a median survival time of about one year, similar to the survival time for dogs treated with amputation and chemotherapy. Up to 16–28% of dogs are alive at two years.3
The median survival time for dogs with amputation alone is about three months.4
Meet Our Osteosarcoma Pet Heroes
Here are a few our inspiring Pet Heroes that have fought bone cancer. We invite you to read their stories. If your pet was diagnosed with osteosarcoma, contact the nearest PetCure Oncology location near you. Our board-certified veterinary oncologists can discuss the specifics with you and help you decide on the best treatment for your pet and your family.
- Pet Hero: Rufus the Big Lovable Mastiff Mix
- Pet Hero: Mandie the Therapy Dog Inspires Others
- Pet Hero: Mischevious Dylan Receives a Bone Cancer Miracle (cat)
- Pet Hero: Sundance Walks Again Following Cancer Treatment (chondrosarcoma)