🔬 What Is Osteosarcoma?

Osteosarcoma is the most common bone cancer in dogs, especially affecting the legs of larger breeds. It typically strikes middle-aged to older dogs, but younger dogs—especially in giant breeds—are also at risk. The tumor grows from deep within the bone, gradually destroying it and causing significant pain. 🧬

📍 Where It Appears

• 🐾 75–85% of cases occur in the limbs (appendicular osteosarcoma)
• 🦷 Other locations include ribs, jaw, spine, and pelvis (axial osteosarcoma)

As the tumor grows, swelling develops, and the bone weakens, often resulting in a pathologic fracture—where the bone breaks due to the tumor’s damage rather than trauma.

🩻 How Is It Diagnosed?

Radiographs (X-rays)

Veterinarians look for a "sunburst pattern" and lytic bone lesions. A broken bone that won’t heal is also a strong indicator of bone cancer.

Needle Aspirate or Biopsy

Though X-rays are often diagnostic, confirmation via tissue sample is standard:

• Needle aspirate – Less invasive, collects cells for analysis
• Biopsy – Surgically removes a bone core; more invasive and painful

🩺 Staging: Has It Spread?

Osteosarcoma is considered to have already spread by the time it's diagnosed—even if invisible. Chest X-rays check for lung metastases, the most common site of spread. CT scans or bone scans may be recommended to look for other affected sites.

⚠️ Conditions That Mimic Osteosarcoma

• Chondrosarcoma – Often affects ribs or skull
• Squamous cell carcinoma – Arises in jaw or toe bones
• Synovial cell sarcoma – Spans both bones of a joint
• Fungal bone infections – Rare, but seen in endemic areas (e.g., Valley Fever)

💥 Treatment Goals: Pain & Cancer Control

The priority in osteosarcoma management is twofold:

• ✅ Relieve pain (through amputation, radiation, or medications)
• ✅ Slow or stop metastasis (via chemotherapy)

🦿 Amputation: Fast & Definitive Pain Relief

Removing the affected limb provides immediate and total pain relief. Many owners worry, but dogs adapt quickly and return to running, playing, and enjoying life—especially if the other legs are healthy.

⚠️ Amputation may not be advised if arthritis is severe or metastasis is advanced.

🦾 Limb-Sparing Surgery

• Removes tumor bone while preserving the leg
• Often uses bone grafts or stimulates new bone growth
• Only suitable for specific locations (like the radius)
• Requires chemotherapy and long recovery time

🔦 Palliative Radiation + Bisphosphonates

If surgery isn't an option, radiation therapy can reduce pain for 2–4 months. It's often combined with bisphosphonates like pamidronate or zoledronate to help preserve bone and manage pain.

💊 Pain Medications

• NSAIDs: Carprofen, deracoxib, meloxicam
• Narcotics: Tramadol, codeine-based meds
• Gabapentin: Neuropathic pain support
• Amantadine: Helps reduce chronic “wind-up” pain

These meds help but rarely suffice on their own for long-term comfort. Amputation or radiation is still key for pain control. 💉

🧬 Chemotherapy: Fighting the Spread

Since osteosarcoma spreads rapidly, chemotherapy is vital after surgery or with radiation. Options include:

Cisplatin (IV x3)

• 🧪 400-day median survival
• 💔 Toxic to kidneys

Carboplatin (IV x4)

• 💉 Similar survival to cisplatin
• ✅ Safer for kidneys

Doxorubicin (IV x5)

• ❤️ Can affect heart function
• 🧬 Requires pre-treatment cardiac screening

Cisplatin + Doxorubicin Combo

• 📈 48% 1-year survival
• ⏳ 16% survive 3 years

💡 What About Side Effects?

Dogs handle chemotherapy better than people. Most experience only mild lethargy or nausea for 1–2 days post-treatment. Medications like ondansetron (Zofran) reduce these effects. Hair loss is rare but may occur in breeds with continuously growing coats like poodles and terriers.

🦴 Axial Osteosarcoma (Non-Limb Bones)

• Often slower-growing
• More insidious—may go undiagnosed for months
• 💀 Jaw osteosarcoma can be treated surgically without chemo in some cases
• Rib osteosarcoma is more aggressive

📊 Prognosis Summary

🧭 Making the Best Decision

This cancer progresses fast. Early diagnosis, prompt pain control, and appropriate staging help guide your decisions. Whether you choose surgery, radiation, or medical care alone, what matters most is comfort and quality of life.

🔧 Ask A Vet Can Help

Need help navigating the choices? Book a consult with Ask A Vet for second opinions, pain management advice, or chemo support. We’re here to guide you and your pup through the hardest decisions with knowledge and compassion. 💙

🐾 Final Thoughts from Dr Duncan Houston

Osteosarcoma is a challenging diagnosis, but your dog can still live with love, activity, and joy. Whether you choose amputation, chemo, or comfort care—you're doing what's best. Your choices, paired with timely care, mean everything. ❤️🐶