![](https://cdn.sanity.io/images/0vv8moc6/dvm360/5f5752c00a03f343490306c3d6b4518b22939990-4421x2928.jpg?fit=crop&auto=format)
Appendiceal osteosarcoma is the most common malignant primary canine bone tumor and is typically found in large to giant dog breeds. When treated with amputation or tumor removal only, median survival times (MST) do not exceed 5 months, with the majority of dogs suffering from metastatic disease.1 Craig A. Clifford DVM, MS, director of DACVIM (oncology) at BluePearl Science, said osteosarcoma (OSA) accounts for approximately 90% of appendicular bone tumors in dogs and 2% to 7% of all tumors in dogs. dog.2 Due to the prevalence of this disease in dogs, Clifford explained how to diagnose and treat this type of cancer to attendees at the Directions in Veterinary Medicine symposium in Nashville, Tennessee.
Diagnostic
Clifford said lameness and localized swelling of the limbs are the most common complaints he receives with appendicular OSA. He recommended performing a thorough orthopedic examination to locate the source of the lameness and differentiate metaphyseal pain from other orthopedic conditions common in large breed dogs, such as cranial cruciate ligament rupture and hip dysplasia.
He told attendees: “Seeing these cases first, we all know that the genetic influence of these, (we will see) large breed and giant dogs, come to you for lameness. Naturally, you don’t think of osteosarcoma right away. They’re going to be treated in a supportive way: a little rest, some NSAIDs (non-steroidal anti-inflammatory drugs), and then they get a little better, but then they get worse and come back to you. So at this point, some of the things to look at will be the signal. Where are they lying? We know that front legs are more common than back legs. Location number 1 is the distal radius, (number) 2 is the proximal humerus, then 3 and 4 are around the knee. Finding lameness along these areas will definitely increase (a potential diagnosis of OSA).
X-rays
Clifford recommended using radiographs to make a tentative diagnosis of primary bone tumor and differentiate it from other orthopedic diseases. On this x-ray, veterinary professionals will most likely see cortical lysis, the exterior of the bone will have very visible bone destruction. Trabecular lysis, the structure of the inner part of the bone, will also be seen and is quite common with OSA. The bone may be laid down abnormally.
“The other thing we can see is the appearance of the sun. And for those of you who haven’t seen this before, it’s basically some kind of tumor invading the soft tissue.
Bone biopsy
A bone biopsy may be performed to confirm the diagnosis of OSA using a Jamshidi needle but is not necessarily required before treatment. Clifford mentioned the problem with the biopsy, if it’s the distal radius, is that it could further weaken the bone. Clifford recommended biopsying the center rather than the periphery.
Aspire
“The other thing that can be done and this is the one I suggest is the idea of sucking it up. We and others have published (studies) on this and aspiration gives us a high probability (of a correct diagnosis),” Clifford said. “Every clinic now has ultrasounds. So I think it’s very easy to do.
If the aspiration is inconclusive or the client decides against it, Clifford recommends using the PetDx OncoK9 liquid biopsy test.
Blood tests
Clifford said that with each of these techniques and options, blood work, a complete blood count and a chemistry panel should be done first and foremost. “Alkaline phosphatase (ALP) has been shown to be one of the strongest indicators of this disease. If it is higher than normal, it is associated with a poor prognosis. So you will already have information that will help the owner make decisions when they are in your office. Something to keep in mind, doing a chemistry panel of blood tests to make sure they are OK for anesthesia, but also looking at the ALP level. Clifford also mentioned that if the monocyte or lymphocyte count is higher than normal, some studies have shown that this is also associated with a poor prognosis.
Clifford also recommended sending chest x-rays to a radiologist to check for anything that might have been missed. “An owner won’t have a problem paying to have a radiologist look at them, because there’s a lot that depends on something like that, it’s going to make or break the deal.”
Treatment
Appendiceal OSA is a highly malignant tumor with over 75% of dogs eventually succumbing to their disease due to distant metastases.1 Often, metastases can determine whether treatment will be curative or palliative. However, less than 15% of dogs have clinically detectable metastases at the time of initial diagnosis. “If there are metastases, that changes everything. We will no longer have the ability to heal this dog. Most dogs that have metastases at diagnosis are asleep within about 4 to 6 weeks. So this is clearly why x-rays are so important beforehand.
Healing intention
Curative treatment will include surgery, including limb amputation, followed by chemotherapy. Clifford said most dogs do well after these treatments.
Palliative
“The other option is more palliative. So with palliatives, we cannot cure them. But what can we do is maintain or help control the pain because the main reason a dog is put to sleep with osteosarcoma is due to pain and this usually happens within about 2 months. These palliative options include analgesia, radiotherapy and limb amputation (without being followed by chemotherapy). All of these treatment options aim to control pain in the patient.
The references
- Boermann I, Selvarajah GT, Nielen M, Kirpensteijn J. Prognostic factors in canine appendiceal osteosarcoma – a meta-analysis. Res. veterinarian BMC. May 15, 2012;8:56. doi: 10.1186/1746-6148-8-56. PMID: 22587466; PMCID: PMC3482154.
- Clifford C. Canine osteosarcoma. Presented at: Guidance in Veterinary Medicine; Nashville, Tenn.; September 15-16, 2023.