Bone Cancer (Osteosarcoma) in Dogs

What is osteosarcoma?
Osteosarcoma in dogs is a malignant cancer of the bone that most commonly affects large and giant breeds such as Golden Retrievers, German Shepherds, Dobermans, Great Danes, Rottweilers, and Saint Bernards. It is most often seen in middle-aged to older dogs and most commonly involves bones of the limb. Other possible locations include the jaw, ribs, nasal cavity, and spine.

Risk factors that predispose dogs to osteosarcoma
While the tendency to develop bone cancer is likely genetic, other hormonal and environmental factors are believed to potentially predispose dogs to develop bone cancer. Increasing weight and height are believed to be risk factors in some dogs. Recent epidemiological studies have shown that sex hormones may have a protective effect on the future development of bone cancer. Dogs that are spayed and neutered before sexual maturity seem to have an increased risk of future bone cancer.

Key facts about osteosarcoma in dogs and cats

• Osteosarcoma is an aggressive, malignant bone cancer that most commonly affects large and giant breed middle-aged to older dogs.
• Signs of osteosarcoma usually involve progressive lameness; local swelling and other clinical signs may also occur depending on the location of the cancer.
• Limb amputation is most commonly used to enhance quality of life, however chemotherapy and/or radiation are also used in certain osteosarcoma cases.
• Prognosis of osteosarcoma depends on whether the cancer has spread to the lungs or other areas.

Symptoms of bone cancer (osteosarcoma) in dogs
The most common clinical signs of dogs with bone cancer are a progressive painful lameness and swelling of the affected limb. While the lameness may be intermittent initially, it often gradually progresses over 1-2 months. With advanced cases, secondary fracture of the underlying bone is possible as well. Other symptoms depend on other areas of involvement and may include nasal discharge, difficulty eating and drinking, and neurological signs.

Diagnosis of bone cancer (osteosarcoma) in dogs
Physical exams and X-rays are most commonly used to make a tentative diagnosis of bone cancer, as most pets will present at an advanced stage with swelling and tenderness of the underlying bone, as well as having characteristic destructive bone changes apparent on X-rays. While history, physical exam, and X-rays often suggest a diagnosis of bone cancer, bone biopsy is the only way of truly confirming diagnosis, and differentiating primary bone tumors from other cancer types. Since bone cancer is often spread to the lungs, it is important to have a chest X-ray on any pet diagnosed with osteosarcoma. CT scans and/or MRIs also may be indicated depending on the primary location of the cancer.

Treatment for bone cancer (osteosarcoma) in dogs
The treatment of choice by veterinarians for most dogs with osteosarcoma of the leg is amputation of the affected limb, after which most dogs do function quite well. Adjunctive chemotherapy and/or radiation may also be given depending on the severity and progression of the cancer at time of diagnosis, and/or whether dog owners allow amputation. Because of the pain associated with this type of cancer, it is often important to treat and ideally prevent pain with medications such as non-steroidal anti-inflammatory drugs (NSAIDs) like Rimadyl or Previcox.

Prognosis for dogs with bone cancer (osteosarcoma)
There are several factors that will determine prognosis, including location of the cancer, and extent and/or spread of disease at time of diagnosis. Pets that have bone cancer that has spread to the lungs have a much poorer prognosis than pets with local osteosarcoma.