Osteosarcoma in Dogs

Canine osteosarcoma is a type of aggressive bone cancer that most commonly affects the limb bones, especially the fore limbs of the middle aged and elderly dogs. The most common victims of this dog cancer are large dog breeds like Rottweilers, Shepherds, Labradors, Dobermans, Great Danes, Saint Bernards, Irish Wolfhounds and Golden Retrievers. The malignant or cancerous tumor develops deep within the bones, and then grows rapidly to destroy the bones from the inside. Osteosarcoma can also metastasize to other parts of the body of the dogs, more commonly to the lungs and other bones of the skeletal system.

Causes of Bone Cancer in Dogs
As has been mentioned already, large and giant dog breeds are at an increased risk of developing osteosarcoma. Moreover, the incidence of the disease has been found to be slightly higher in male dogs than their female counterpart. Though, the exact causes of the diseases are not known, it has been observed that the tumors generally develop in the growth plates. This led to the speculation that the cells of the growth plates have a genetic predisposition for the development of malignant tumors.

Even factors that affect growth rate of the dogs like, especially a diet that can stimulate rapid growth and development, is also thought to play a significant role. Apart from these, other risk factors include, bone fracture as well as bone infections, and exposure to ionizing radiation and chemical carcinogens. Additionally, castrated males and spayed female dogs have been found to be at an increased risk of developing osteosarcoma.

Symptoms of Bone Cancer in Dogs
Osteosarcoma mostly affects the forelimbs of the dogs, that bear much of the body's weight. Sometimes, tumors can also develop in the skull and ribs, and spread to areas like the lungs. The most commonly observed symptoms of this condition are

• Lameness, usually intermittent, but can gradually become permanent, with increased damage of the affected bone/ bones.
• Pronounced swelling of the affected bone.
• Pathological fracture, which is the condition, where bone breaks quite easily due to minor injury.

Apart from these usual symptoms, dogs with osteosarcoma may cough a lot, if the cancer has spread to the lungs.

Treatment for Canine Bone Cancer
Symptoms like lameness and swelling of the bone often necessitate an X-ray or radiography of the affected bones, that reveal the development of tumor and some characteristic bone patterns like, lytic lesion. A confirmed diagnosis, however, is carried out with the help of a biopsy, for which a small section of the affected bone has to be removed. This can be a bit painful for dogs who are affected by the disease.

The most common treatment is amputation, followed by chemotherapy. Sometimes, limb sparing surgery is also carried out, if the tumor has not affected more than 50% of the bone, and also has not spread to the surrounding muscles. In this method, the tumorous bone is removed surgically, and then replaced with bone graft. However, the procedure is not very effective for treating osteosarcoma of the hind legs.

Chemotherapy drugs often prove effective in altering the course of this bone cancer. The most commonly used chemotherapy drugs are, cisplatin, doxorubicin and carboplatin. For providing temporary relief from the pain and discomfort, non steroidal anti-inflammatory medications, as well as, analgesics like, carprofen, butorphanol, aspirin, tramadol, can be used. Radiotherapy can also be used for pain management in osteosarcoma.

Osteosarcoma is a very aggressive form of bone cancer that spreads or metastasizes quite rapidly to other parts of the body. Most cases of this dog illness are diagnosed, when the cancer has already metastasized to other parts. Therefore, any case of lameness in dogs should be evaluated immediately to rule out the possibility of osteosarcoma. As certain breeds of dogs are more prone to develop this type of bone cancer, their owners should remain more vigilant against the disease.