Bone cancer is a common cancer in dogs, and approximately 85% of bone cancers are a type called osteosarcoma. This cancer most often affects large and giant breed dogs and typically arises in the long bones of the legs.
How do I know if my dog has bone cancer?
The first symptom of dogs with osteosarcoma is limping, sometimes accompanied by swelling in the leg. Since there can be multiple causes for limping, your veterinarian may recommend anti-inflammatory pain medications and rest, or they may recommend x-rays. Typically, bones affected with cancer look “moth-eaten” on x-rays because the tumor has destroyed the normal bone. The affected area is called a lytic bone lesion. There also can be abnormal “reactive” bone that has developed around the bone tumor. Often a diagnosis of osteosarcoma is tentatively made based on x-rays, although confirming the diagnosis requires obtaining a sample of the bone tissue.
How is osteosarcoma treated?
Our goal for every patient of the AERC Oncology Service is to provide patients with the highest quality of life for as long possible. There are several treatment modalities for osteosarcoma, but the most key component for this type of cancer is pain management. Any tumor that destroys bone is very painful, so we always assume that dogs with bone tumors are much more painful than they let on.
The most effective and complete way to relieve pain is to amputate the affected limb. Fortunately, animals do not have the emotional attachment to their limbs that humans do. In fact, we find that owners usually have a much harder time with the amputation than their pets do! Amputation gives patients the best chance for a pain-free return to their usual lifestyle, and three-legged dogs can perform virtually any activity a four-legged dog can do. Radiation therapy may also be an option for pets whose owners decline amputation or for which amputation is not an option.
Approximately 90% of dogs with osteosarcoma already have microscopic metastasis (cancer spread) to lungs at the time of diagnosis, even if it cannot be seen on chest x-rays. To help prevent or delay metastasis, chemotherapy is typically performed after surgery or radiation. Fortunately, animals tolerate chemotherapy much better than people typically do. Learn more about chemotherapy in pets here.
What can I do if I choose not to treat my pet’s osteosarcoma?
Your oncology team or your family veterinarian can help you develop the most appropriate palliative care treatment plan for your dog. A pain management protocol will be critical to help maximize your pet’s quality of life and should not be overlooked. Typically, two to four different oral pain medications will be recommended to try to address the intensity of the bone pain. Additional therapies (bisphosphonates, acupuncture) may also be recommended.
What is the prognosis for dogs with osteosarcoma?
The average survival time for dogs who have amputation alone is around four to five months; at that time, most patients will develop visible cancer spread to their lungs on x-rays. The addition of chemotherapy post-amputation can double that to ten to twelve months. Without treatment, most dogs live around three to four months. Dogs who do not have surgery are also at risk for a pathologic fracture (break in the bone) at any time. Pathologic fractures occur in diseased bones and can occur during normal activity, even just from an average walk. Dogs with bone tumors should not engage in high-impact activity (running, jumping) but only amputation will eliminate the risk of fracture.
Osteosarcoma in Cats
We didn’t forget about kitties! Bone cancer in cats is much less common than in dogs, but osteosarcoma is still the most frequently diagnosed type; it also most commonly affects bones in the limbs. While osteosarcoma in cats does cause pain and risk for pathologic fracture as in dogs, it has a lower risk of metastasis in cats. Cats with osteosarcoma that have a limb amputation can live two to four years (and longer!) post-surgery. Chemotherapy after amputation is typically only recommended if there are any worrisome features on the final biopsy results. Pain management is just as important in cats, so if amputation is not pursued, talk to your vet about how to help manage your cat’s pain.
While bone cancer can be a hard diagnosis to hear, there are several treatment options that can help your pet continue living their best life! Talk to your family veterinarian or a board-certified veterinary oncologist to learn more.
Learn more about Animal Emergency & Referral Center of Minnesota’s Oncology Service here!
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