Osteosarcoma is a primary bone tumor; it originates in bone and can spread, or metastasize, to other parts of the body, especially the lungs. Large dogs (over 75 pounds) have a higher tendency to develop osteosarcoma, a type of cancer that originates in bone cells.Large and giant breed dogs such as Newfoundlands, Great Danes, Irish Wolfhounds, Scottish Deerhounds, greyhounds, St. Bernards, large Labradors, and Rottweilers are predisposed for this form of cancer, which usually develops in geriatric dogs over eight years old.  Some breeds show up more often with "osteo", Rottweilers have a 12.5 % chance of making this list in their lifetime. This indicates a genetic component that has to date not been identified.
The first sign owners may notice is a sudden lameness or limping which may or may not be associated with exercise. An owner may notice that their dog is limping after playing, and may suspect the dog sprained its leg.  Veterinarians may start your pet on anti-inflammatory medications. This should reduce swelling and pain. If the pain does not go away or worsens with medical treatment, further diagnostics can help determine if it is osteosarcoma. Veterinarians put osteosarcoma on a rule out list in some dogs with a limp. Breed and age of dog will prompt this thinking.
Radiographs (x-rays), to look for signs of abnormal bone growth, may indicate osteosarcoma. The usual sites for this abnormal growth are the leg (long) bones, away from the elbow or near the knee. In the front leg lesions would be in the radius (foreleg bone) toward the wrist, and the humerus toward the armpit. In the hind limbs the lesions would be in the tibia (shin bone) and femur (thigh bone), close to the knee. Occasionally osteosarcoma is seen in the mandible, (lower jaw bone). I had one case in a Great Dane with osteosarcoma in the metacarpal bones of the front paw (corresponds to the bones that make the palm of your hand).Osteosarcoma cannot be diagnosed just with radiographs alone. Other types of cancers and other conditions can cause bone problems. Proper staging and a rational treatment plan for cancer requires an accurate diagnosis. A tentative diagnosis of osteosarcoma case after radiographs requires the next step of cytology and/or biopsy.A biopsy (surgical removal of a small chunk of tissue) for examination under a microscope is the standard diagnostic test for most types of cancer. Cytology is a less invasive method. This involves inserting a needle into tissue to get a sample of cells. The cells are put on a glass microscope slide and stained for visual examination. Veterinarian pathologists have developed staining techniques that can differentiate osteosarcoma cells from other types of cancer cells. This makes cytology a more accurate diagnostic tool. Cytology is less invasive, less painful, quicker and more appropriate for sampling from thin areas of bone (mandible) that are too delicate for biopsy or may be susceptible to pathological fractures.
Treatment of osteosarcoma mandates surgical removal of the cancerous bone as well as chemotherapy to prevent metastasis to the lungs. If the cancer is caught early, surgery may involve removing just a portion of a bone (referred to as "limb sparing"). Sometimes partial or full amputation of a limb is required. Many dogs can remain active after an amputation.Veterinary oncologists are also investigating treatment combinations of radiation therapy, systemic chemotherapy, and a human cancer drugs are being incorporated in treatment protocols. There are new uses of old drugs and new drugs that are becoming available for veterinarian oncologist to be used in cancer cases. Dr Barb Kitchell, Head of the Michigan State University Veterinary Teaching Hospital Center for Comparative Oncology unit is well versed in cutting edge cancer treatments. Osteosarcoma cure rate, extending life approximately 2 years, still hovers in the 20% rate. Limb amputation, radiation and chemotherapy may only give five months of life expectancy. Not amputating and no chemo, no radiation may give approximately five months of life.  These are not very exciting choices.

If your dog has osteosarcoma you need to understand there is a difference in treatment outcomes. Veterinary medicine helps with extending "quality of life" more than a push for a cure in individual cases. Radiation and chemotherapy are used less aggressively in animals to minimize side effects and ensure that the pet has an enjoyable quality of life.

You may wonder why I picked the topic of osteosarcoma for this article. I have given the specifics for a very deadly disorder. You now know the facts. I am in the position to take the advice I have been dispensing for 35 plus years. Those sayings are supposed to give comfort to owners, but they leave me empty when it is in reference to my dog Clover. Clover is a 5 ½ year old, spayed female, Irish Wolfhound. She has osteosarcoma above her left carpus (wrist), with some radiographic lesions visible on chest radiographs. Clover is scheduled for evaluation at the MSU Animal Cancer Center July 1, 2008. I have become a "client" that wonders am I doing the right thing for Clover or myself. It gets down to the question. Do I want a dog or this dog? I am voting to keep this dog Clover. As long as she can have a reasonable expectations of a quality life and contributing to myself and the people she loves. You understand the importance of the animal human bond or is it the human animal bond that is strongest.

For more detailed information about osteosarcoma, consult your veterinarian.

Michael Sweet, D.V.M.
6/27/2007