Bone Cancer in Dogs: Understanding Canine Osteosarcoma

Bone cancer in dogs, also known as canine osteosarcoma, is a serious and aggressive condition that affects the bones, most commonly the long bones of the limbs. Osteosarcoma can significantly impact your dog’s quality of life, but understanding the symptoms, causes, and available treatments can help you make informed decisions about your pet’s care. This article provides a comprehensive overview of bone cancer in dogs, including its symptoms, diagnosis, treatment options, and prognosis.

What is Osteosarcoma?

Osteosarcoma is a malignant tumour that originates from immature bone cells called osteoblasts. It is the most common type of bone cancer in dogs, accounting for about 85% of all skeletal tumours. This cancer typically affects the long bones of the limbs, such as the femur, tibia, and humerus, but can also occur in the skull, spine, ribs, and pelvis. The disease is known for its aggressive nature and its tendency to spread to other parts of the body, particularly the lungs.

Symptoms of Bone Cancer in Dogs

Bone cancer in dogs can present with various symptoms, some of which may be subtle or mistaken for other conditions. Common signs include:

• Lameness or Limping: Persistent lameness in one limb, often worsening over time.
• Swelling or Mass: Noticeable swelling or a lump on the affected bone.
• Pain and Tenderness: Pain in the affected area, which may cause your dog to react when touched.
• Reluctance to Exercise: Reduced activity levels or unwillingness to play.
• Loss of Appetite and Weight Loss: Decreased interest in food and noticeable weight loss.
• Dehydration: Signs of dehydration, such as dry gums and sunken eyes.
• Tachycardia: Rapid heart rate due to pain or distress.
• Lethargy: General fatigue and lack of energy.
• Fractures: Pathologic fractures or breaks in the affected bone due to weakened structure.

In advanced stages, if the cancer has metastasized to the lungs, your dog may show signs of respiratory difficulties, such as coughing or laboured breathing.

Causes and Risk Factors of Bone Cancer in Dogs

The exact cause of bone cancer in dogs is not fully understood, but several factors may contribute to its development:

• Genetic Predisposition: Certain breeds are more likely to develop osteosarcoma, suggesting a hereditary component. Breeds with a higher risk include:
  • Rottweilers
  • Great Danes
  • Irish Wolfhounds
  • Great Pyrenees
  • Newfoundlands
  • Bernese Mountain Dogs
  • Saint Bernards
  • German Shepherds
  • Weimaraners
  • Boxers
  • Greyhounds
  • Irish Setters
  • Doberman Pinschers
  • Golden Retrievers
• Age: Osteosarcoma is most commonly seen in middle-aged to older dogs, particularly those between seven and ten years old. However, it can also occur in younger dogs, especially large and giant breeds.
• Environmental Factors: Previous bone injuries, fractures, and exposure to ionizing radiation may increase the risk of developing bone cancer.

Diagnosing Bone Cancer in Dogs

Proper diagnosis is crucial for effective treatment. Your veterinarian will perform a series of tests to confirm the presence of osteosarcoma and assess its extent:

• Physical Examination: Your vet will examine your dog’s overall health and check for swelling or masses in the affected area.
• Radiographs (X-rays): X-rays can reveal characteristic changes in the bone, such as destruction and new bone formation.
• Biopsy: A sample of the tumor tissue is collected and analyzed under a microscope to confirm the diagnosis of osteosarcoma.
• Advanced Imaging: CT scans or MRIs may be used to get detailed images of the tumor and plan for surgery if needed.

Treatment of Bone Cancer in Dogs

Once diagnosed, several treatment options may be considered based on the tumor’s location, size, and stage:

1. Surgery: The primary treatment for osteosarcoma is surgical intervention. Amputation of the affected limb is the most common approach and can be effective in providing pain relief and improving quality of life. Many dogs adapt well to life on three legs. If amputation is not feasible, limb-sparing surgery might be an option, involving the removal of the cancerous section of bone and its replacement with a bone graft or metal implant.
2. Chemotherapy: After surgery, chemotherapy is often used to target any remaining cancer cells and reduce the risk of metastasis. Common chemotherapy drugs for osteosarcoma include cisplatin, carboplatin, and doxorubicin.
3. Radiation Therapy: This treatment can help manage pain and slow tumor growth, especially if surgery is not an option. Radiation targets cancer cells directly, reducing tumor size and providing pain relief.
4. Pain Management: Controlling pain is a critical aspect of the treatment plan. Your veterinarian may prescribe medications such as NSAIDs, opioids, gabapentin, and bisphosphonates to manage pain and improve comfort.

Prognosis of Bone Cancer in Dogs

The prognosis for dogs with osteosarcoma varies depending on several factors:

• Location and Stage: Tumours located in limbs may have a different prognosis compared to those in other bones. Early-stage treatment often has a better outcome.
• Treatment: Dogs treated with amputation followed by chemotherapy generally have a median survival time of 10-12 months. Some dogs may live up to two years or longer. Without treatment, the median survival time is typically around four months due to the rapid spread of the disease.
• Individual Response: Outcomes vary based on how well the dog responds to treatment and how effectively pain is managed.

Making Decisions About Treatment

Choosing the best course of action for your dog involves weighing the potential benefits and risks of various treatments. Some pet owners may decide against aggressive treatments, opting instead for palliative care to maintain their dog’s quality of life. Your veterinarian will guide you through the decision-making process, considering your dog’s specific needs and circumstances.

Support and Resources

Receiving a diagnosis of bone cancer can be overwhelming. Seek support from friends, family, or pet support groups to help you through this challenging time. Educating yourself about the condition and working closely with your veterinarian can make a significant difference in managing your dog’s care.

Conclusion

Bone cancer in dogs, or osteosarcoma, is a severe and aggressive condition that requires prompt and comprehensive treatment. Understanding the symptoms, causes, and treatment options can help you make informed decisions about your pet’s health. By working closely with your veterinarian, you can develop a plan to manage your dog’s condition and provide the best possible quality of life. Remember, every dog’s situation is unique, and your veterinarian is the best resource for personalized advice and support.