Osteosarcoma (OSA) is the most common type of bone cancer in dogs, accounting for around 85% of all primary bone tumors. This aggressive cancer primarily affects the long bones, such as the femur, tibia, and humerus, but it can also occur in other bones. Osteosarcoma in dogs is highly malignant, meaning it grows quickly and often spreads to other parts of the body, most commonly the lungs.
What is Osteosarcoma?
Osteosarcoma is a form of cancer that originates in the bone’s osteoblasts, which are the cells responsible for forming new bone tissue. This cancer is characterized by the production of abnormal bone tissue and tends to spread rapidly to other parts of the body. While the tumor starts in the bone, it can metastasize, usually to the lungs, and sometimes to other bones and organs.
Causes and Risk Factors
The exact cause of osteosarcoma in dogs is not fully understood, but several factors may contribute to the development of this aggressive cancer:
- Age: Osteosarcoma typically affects older dogs, with the majority of cases occurring in dogs over 7 years of age.
- Breed: Large and giant dog breeds are more likely to develop osteosarcoma. Breeds such as the Rottweiler, Golden Retriever, Labrador Retriever, Great Dane, and Irish Wolfhound are particularly prone to this type of cancer.
- Gender: Male dogs are at a slightly higher risk of developing osteosarcoma than females.
- Previous bone trauma: While bone fractures or injuries don’t directly cause osteosarcoma, some researchers suggest that chronic trauma or inflammation to the bone might increase the risk of developing bone cancer.
- Genetic factors: Certain genetic factors may predispose dogs, particularly larger breeds, to develop osteosarcoma.
Symptoms of Osteosarcoma in Dogs
The signs of osteosarcoma in dogs can vary depending on the tumor’s location, but common symptoms often include:
- Lameness or limping: This is usually the first noticeable symptom. The dog may start favoring one leg and avoid putting weight on it. Lameness tends to be worse after exercise or activity and may improve with rest.
- Swelling or a visible lump: A visible swelling or mass may form over the affected bone. This is often seen at the site of the tumor and may be warm to the touch.
- Pain and sensitivity: Osteosarcoma is painful due to the bone destruction it causes. The dog may react to touch, especially around the affected area, and show signs of discomfort, such as whining or yelping.
- Changes in behavior: Dogs with osteosarcoma may exhibit behavioral changes, such as reluctance to move or play, irritability, or loss of appetite.
- Weight loss: As the cancer progresses, dogs may lose weight due to pain, reduced activity, and a decreased appetite.
- Respiratory distress: If the cancer has spread to the lungs (a common site for metastasis), the dog may show signs of respiratory distress, such as coughing, labored breathing, or rapid breathing.
Diagnosing Osteosarcoma
If osteosarcoma is suspected, the veterinarian will perform a thorough physical exam and may recommend the following diagnostic tests:
- X-rays: Radiographs (X-rays) are typically the first diagnostic tool used. They can reveal characteristic bone lesions associated with osteosarcoma, such as bone destruction, abnormal bone growth, and the formation of new bone in response to the tumor.
- CT or MRI scans: These imaging techniques can provide more detailed views of the tumor and help determine the extent of the cancer and whether it has spread.
- Biopsy: A biopsy involves taking a tissue sample from the tumor to confirm the diagnosis. This is usually done through a needle aspiration or surgical biopsy.
- Bone scans: A bone scan can help identify areas of abnormal bone activity and determine if the cancer has spread to other bones.
- Blood tests: Blood tests may be performed to assess the dog’s overall health, but they are not typically diagnostic for osteosarcoma itself.
Treatment Options for Osteosarcoma in Dogs
Due to the aggressive nature of osteosarcoma, early diagnosis and prompt treatment are crucial. Treatment options for osteosarcoma in dogs generally aim to reduce pain, slow the tumor’s growth, and improve the dog’s quality of life.
1. Surgery
Surgical removal of the tumor is the most effective treatment for osteosarcoma, especially if the tumor is localized to one bone. Amputation of the affected limb is often recommended in cases where the cancer is limited to the limb. While amputation may seem drastic, many dogs recover well after surgery and can live normal, pain-free lives, especially with proper rehabilitation. Dogs are generally able to adapt to life with three limbs, particularly large dogs like Rottweilers and Golden Retrievers.
In some cases, if amputation is not an option, limb-sparing surgery may be attempted, where the tumor is removed, and the bone is reconstructed using metal plates or other materials. However, this option is less common and carries a higher risk of complications.
2. Chemotherapy
Chemotherapy is commonly used after surgery to reduce the risk of metastasis, as osteosarcoma has a high potential to spread, particularly to the lungs. Chemotherapy helps kill any remaining cancer cells that may have spread beyond the bone. While chemotherapy is not a cure, it can extend survival time and improve quality of life by reducing pain and slowing tumor growth.
The most commonly used chemotherapy drugs for osteosarcoma are carboplatin and doxorubicin. Chemotherapy is often given in cycles over several weeks or months, and side effects like vomiting, diarrhea, and loss of appetite may occur, but they are usually temporary.
3. Radiation Therapy
Radiation therapy can be used to help shrink the tumor and alleviate pain, particularly if the tumor is inoperable or if the cancer has spread to other bones. It is typically used in conjunction with surgery and chemotherapy to improve the effectiveness of treatment.
4. Palliative Care
If the cancer is too advanced for surgery or chemotherapy, palliative care may be recommended to keep the dog comfortable. This can include pain management, nutritional support, and treatments to maintain mobility. Medications like NSAIDs (nonsteroidal anti-inflammatory drugs) and opioids may be prescribed to help control pain.
Prognosis
The prognosis for dogs with osteosarcoma varies depending on several factors, including the tumor’s location, the success of surgery, and whether the cancer has spread. The average survival time for dogs with osteosarcoma after amputation is typically 12 to 18 months, especially if chemotherapy is used. However, if the cancer has already metastasized, the prognosis may be more guarded, with survival times generally ranging from 6 to 12 months.
Preventing Osteosarcoma
Currently, there is no known way to prevent osteosarcoma in dogs, but maintaining overall health through proper nutrition, exercise, and regular veterinary check-ups can help manage the risk of many diseases, including cancer.
Conclusion
Osteosarcoma in dogs is a serious and aggressive cancer that requires prompt diagnosis and treatment. While the prognosis for osteosarcoma can be poor, especially if the cancer has spread, surgery and chemotherapy can significantly improve the quality of life and extend survival time for affected dogs. Early detection and appropriate treatment are key to helping your dog live a longer, pain-free life. Always consult with a veterinarian if you notice any signs of illness, and discuss the best treatment options for your dog’s specific condition.
