The most common type of bone tumor seen in dogs is
osteosarcoma. Typical clinical signs include a progressive lameness (limp) in an
older, large breed dog in association with a swelling or pain in a long bone.
Certain breeds appear to have a genetic predisposition for development of
osteosarcoma , including the Irish wolfhound, Rottweiler, and retriever breeds.
The radiographic appearance of mixed bone destruction and excessive bone
production in a succeptible breed is highly suggestive of this diagnosis, but
suspicious areas can be confirmed by a needle biopsy performed under a brief
anesthetic. Chest x-rays or computerized tomography (CT s
can) are required to assess for metastasis (spread of the
tumor) to the lungs. Bone cancer is typically malignant and is rarely cured by
surgical therapy. Thus, therapy is directed at two goals: 1) pain relief by
surgical removal of the bone tumor and 2) slowing the spread of the tumor by
administering chemotherapy. The most common palliative surgery performed in dogs
with bone cancer affecting one of the leg bones is amputation of the affected
limb. Although many pet owners are hesitant to perform amputation surgery on
their dogs, postoperative surveys show that 80-90% of people are happy that they
made the decision and would do so again, if required in future pets. For dogs
with concurrent orthopedic or neurologic problems that would make them poor
candidates for amputation surgery, various “limb sparing” te
chniques are available, which involve local removal of the
affected bone and replacement with various metallic or bone implants. Radiation
therapy may also be used to control pain and local tumor growth. Survival
statistics for dogs with osteosarcoma is well described and averages
approximately 5 months without chemotherapy and 12 months with chemotherapy.
Dogs will typically develop evidence of heavy breathing or coughing as
metastasis of tumors occurs in the lungs. Dogs that do not receive pain
relieving surgery can be treated with various analgesic drugs, but these drugs
have limited efficacy and owners will often decide that quality of life is not
acceptable after several weeks. Weakening of the bone in the location of the
tumor may also predispose to pathologic fracture, causing sudden increase in
discomfort and difficulties with medical management.
