Osteosarcoma is a primary bone cancer. This means that the cancer originates in the bone and then metastasizes (spreads) elsewhere. It is a very aggressive disease and statistics show that by the time the primary tumour is removed, 85-90% of cases have metastatic disease.
Signs & Symptoms
Frequently, the dog presents with lameness with or without other signs such as lethargy and weight loss. Many owners notice their dog limping and assume it has hurt itself whilst playing. Rapid, progressive lameness needs an urgent consultation with a vet, especially in older dogs (over 7 years). On palpation, muscle wasting (atrophy), swelling and increased heat and sensitivity are often detected. In the front legs, tumours are frequently located AWAY from the elbow, near the shoulder in the upper humerus, or close to the wrist in the distal radius. In the back legs, tumours are located CLOSE to the stifle in the lower femur and upper tibia. It is not uncommon for bones to suddenly break with minimal trauma as a result of the tumour. This is often the first sign that there is a problem. The signs, symptoms and the appearance of the bone on x-ray are all used to diagnose the disease.
X-ray is often the best diagnostic tool to use for finding bone cancers. When x-ray findings are very characteristic of osteosarcoma, your vet may be confident with using an x-ray alone for diagnosis. However, if the x-ray is not clear or the pain is coming from a very unusual site, your vet may recommend a fine needle aspirate (bone biopsy). This is where a small sample of cells is taken and studied under the microscope in order to determine cell type. Biopsy is used on uncharacteristic lesions, especially if curable conditions exists like infections and bone cysts.
Unfortunately, osteosarcoma is a very nasty and aggressive cancer with over 85% of cases having metastasized by the time the primary tumour is removed. Treatment options are limited due to the aggressive nature of the disease but include pain relief, amputation and chemotherapy. Pain relief may work for a limited period but failure to control severe pain often leads to the owner choosing to euthanise their pet. Limb amputation is the most frequently offered surgical treatment, with or without chemotherapy. The primary goal is pain relief and when amputation is offered alone, only 10% of cases will survive a year or more, with the median survival time being 6 months. Chemotherapy is often offered in conjunction with amputation, with 1-year survival rates increasing to between 35-50%. Chemotherapy in dogs is well tolerated by most but many owners believe their animals will suffer nasty side effects such as nausea and vomiting – side effects often associated with chemotherapy in humans. Interestingly, dogs rarely experience these symptoms. Unfortunately, the cost associated with chemotherapy and the ultimate lack of cure often results in owners declining chemotherapy treatment.
Whilst I know this topic is very close to many of you, it is so important that everyone knows what signs and symptoms to look for. If you have ANY concerns about your dog, please take it to your vet immediately. Don’t forget – nearly all dogs with lameness will not have bone cancer!! That said, if in doubt, get your animal checked out.
If you have any questions or concerns, please call me on 0423 493 130 or email me at firstname.lastname@example.org.
Lynne Harrison BSc (Hons) Phty, MSc (Vet. Phty)
APAM MCSP ACPAT Cat.A