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Osteosarcoma

Osteosarcomas account for only 5 percent of all tumors in dogs, but the cancer has a very high risk of spreading, particularly to the lungs. It is rare in small dogs (

Symptoms

  • Tumors lacated near the ends if the long bones of the legs
  •  Pronounced bone swelling
  •  Fracture at the tumor site
  • Pain or lameness

Breeds at Risk

  • Bernese Mountain Dogs
  • Labradors
  • Boxers
  • Newfoundlands
  • Dobermans
  • Saint Bernards
  • Golden Retrievers
  • Rottweilers
  • Great Danes
  • Shepherds
  • Great Pyrenees
  • Weimaraners
  • Irish Wolfhounds
  •  Greyhounds
Diagnosis
 
Diagnosis usually begins with a complete orthopedic and neurologic examination to rule out other causes of lameness, a physical examination and regional x-rays. X-rays often reveal a characteristic bone-destructive pattern that, coupled with the dog’s medical history and breed, may indicate the development of bone cancer. The great majority of bone tumors will have spread to the lungs by the time of diagnosis, although metastases don’t usually show up on a routine chest x-ray because of their small initial size. Therefore, most dogs with osteosarcoma are treated as if they have metastases to the lungs.

Osteosarcoma will occasionally show up in places other than bone, and likewise other tumor types can initially appear to be an osteosarcoma. A biopsy is recommended if there is any uncertainty about the diagnosis. Because fungal bone infections that are common in certain geographic regions of the country can produce similar symptoms and appearance on an x-ray, a fungal culture or titer is sometimes performed as well.

Another diagnostic test that may be performed is a bone scan, which requires an overnight stay in the hospital after injection of a radioactive tracer. The scan helps determine whether the tumor has spread to other bones and how much of the bone near the primary tumor is affected.

Treatment

Once the tumor has been positively identified as an osteosarcoma, the dog’s affected limb is usually amputated. After the amputation, a course of chemotherapy is usually begun. The most successful drugs are carboplatin and cisplatin. Carboplatin is more expensive but safer and easier to administer than cisplatin. Doxorubicin is another useful compound that is sometimes combined with carboplatin.

Because osteosarcomas are very painful, before amputation pain management is part of the treatment protocol. This can include pain-relieving medications and radiation. Although irradiation of the bone tumor does not significantly affect the pulmonary metastases, it does decrease pain and can greatly improve the quality of life in many dogs.

In rare cases where the tumor is small and in a location where it can be easily removed, some limb-sparing surgeries can be performed. This type of surgery involves removing the affected bone and replacing it with a bone graft that is then plated. Potential complications with this procedure include the development of infection, tumor recurrence and failure of the bone graft to "take."

Prognosis

The life expectancy of a dog with a properly identified and treated osteosarcoma varies greatly but can approach a year or longer. The spread of osteosarcoma to the lungs or other organs is the most common cause of death in dogs.

Current Research

Click here to find out about Morris Animal Foundation--funded research into osteosarcoma.

Disclaimer
Morris Animal Foundation urges pet owners not to implement any suggestions on animal health treatments without prior consultation with their licensed veterinarian. If your pet is experiencing health issues, contact your licensed veterinarian. The Foundation funds research to enhance medical options available to veterinary professionals and their patients.