General Information About Osteosarcoma:
Osteosarcoma is a malignant cancer originating form bone cells. It is possible to have it develop in soft tissues, but this is rare. The classic case of osteosarcoma is a large-breed dog with a firm, painful swelling over the ends of long bones – away from the elbow and toward the knee. X-rays reveal bone with a “moth-eaten” appearance and a “sunburst” pattern. Bone tumors are very painful, and limping is the most common sign.
Definitive diagnosis comes from taking a biopsy of the affected bone and having it examined in a laboratory.
Amputation without chemotherapy can be performed. This is rarely chosen as it is a major surgery with little increase in life span, although it does increase comfort. Likewise, chemotherapy without amputation is rarely performed due to no measurable increase in survival time.
If a patient with osteosarcoma is not a candidate for amputation (such as a dog with severe arthritis in the other legs), treatment is composed of aggressive pain control, and exercise restriction to try to prevent a fracture from occurring at the tumor site. A drug called pamidronate is commonly used. It was developed for use in women to slow the progression of osteoporosis. It is not a chemotherapeutic agent, but rather it slows down the activity of the cells that decalcify and break down bone, and appears to provide a significant improvement in pain control for our patients. As a bonus, it may slow the progression of the tumor growth, although this has yet to be definitively proven. It is given as an intravenous injection over several hours in the hospital once every 21 – 28 days.
Other drugs used to control pain include the non-steroidal anti-inflammatory drugs, and a variety of analgesics. These drugs are tailored to the needs and health of each patient.
With pain management alone, the pain can progress within weeks to a couple months to the point where there is no quality of life, and many families elect euthanasia. With the addition of pamidronate the quality of life is significantly better, and therefore it takes longer until the pain interferes significantly. With amputation alone, or pamidronate without amputation, median survival is about 6 months and the end is reached when pulmonary metastases develop significantly. Somewhere between 10 – 20% of patients live to 1 year, and essentially none make it to 2 years. With amputation and chemotherapy, median survival is about 12 months, with 7 – 21% of patients surviving to 2 years.