What is osteosarcoma?
Osteosarcoma (OSA) is the most common primary malignant bone tumour in dogs β accounting for 85% of all bone tumours. It is a highly aggressive cancer with a strong tendency to metastasise, primarily to the lungs. It predominantly affects large and giant breeds, most commonly in the long bones of the limbs.
Risk factors and breeds
- Most commonly affected breeds: Saint Bernard, Irish Setter, Dobermann, Great Dane, Labrador Retriever, Golden Retriever, Boxer, German Shepherd.
- Typically affects middle-aged to older dogs (7β10 years), but can occur earlier in giant breeds.
- Typical location: appendicular (limbs) in 80% of cases β distal radius, proximal humerus, proximal tibia, distal femur. The clinical mnemonic: "Away from the elbow, close to the knee."
Signs
- Progressive lameness: a limp that doesn't improve with rest and gets progressively worse.
- Swelling or palpable mass at the affected bone site.
- Pain: osteosarcoma is extremely painful. Dogs may refuse to walk, appear depressed, or refuse to bear weight.
- Pathological fracture: the tumour weakens bone structure β some cases are first diagnosed after a spontaneous fracture.
Diagnosis
- X-rays: show the characteristic "sunburst" pattern of bone destruction and periosteal reaction.
- CT scan: for local extent and staging.
- Chest X-rays or CT: to detect pulmonary metastases (present in 80β90% of cases at diagnosis, though often not yet visible on plain X-ray in the early stages).
- Biopsy: definitive histological confirmation.
Treatment options
Amputation + chemotherapy (gold standard)
Amputation removes the primary tumour and eliminates the pain focus. Post-operative chemotherapy (carboplatin or cisplatin-based protocols) delays metastasis. Median survival with amputation + chemo: 10β12 months. 20β25% of dogs survive beyond 2 years.
Limb-sparing surgery
In selected cases, bone segment replacement (prosthesis or bone graft) preserving the limb. Higher complexity, more complications, but comparable outcomes to amputation in specialised hands.
Palliative radiation therapy
For pain control when surgery is not possible or declined. Does not cure but can meaningfully improve quality of life for months.
Palliative medical management only
Chemotherapy without surgery: median survival 4β5 months. Palliative care only (NSAIDs, pain management): 1β3 months.
Life quality after amputation
Dogs adapt remarkably well to three limbs. Recovery is often rapid, particularly in younger animals in good overall condition. Most owners are surprised by how well their tripawd copes β and how quickly quality of life returns.