Osteosarcoma (Bone Cancer)

What is it?

Osteosarcoma starts when the cells that build and remodel bone grow abnormally and form a tumor. It usually develops in the long bones of the legs, especially near the wrist and below the knee, but it can also affect the skull, jaw, ribs, pelvis, spine, or toes. Large breeds are most often affected, including boxers, Doberman pinschers, golden retrievers, German shepherds, Great Danes, greyhounds, Irish wolfhounds, rottweilers, and Scottish deerhounds.

What signs should I watch for?

Osteosarcoma is very painful. With a leg tumor, look for limping, a firm swelling that may feel warm, tiredness, poor appetite, and reluctance to walk or play. A jaw tumor can cause jaw swelling, trouble opening the mouth, drooling, and reluctance to eat. Tumors in the skull or spine cause swelling and pain in those areas.

How is it diagnosed and treated?

Your veterinarian will examine the area and take X-rays, where the bone often looks moth-eaten. A needle sample or bone biopsy confirms the diagnosis, and staging tests such as chest X-rays and bloodwork look for spread. Amputating the affected leg removes the painful tumor, and most dogs adapt very well. Chemotherapy is nearly always recommended afterward, and some forms of radiation therapy are also options. Good pain control is essential throughout.

Can it be prevented, and what's the outlook?

• There is no known way to prevent osteosarcoma.
• It is extremely aggressive: about 90 to 95% of dogs have microscopic spread at diagnosis.
• Treatment aims to relieve pain and control the disease for as long as possible, and dogs usually tolerate chemotherapy well.
• Have any limp that does not resolve, especially in a large-breed dog, checked promptly.