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Osteosarcoma Diagnosis and Treatment Often, the initial complaint before diagnosis is lameness and pain associated with a recent mild trauma. And many times, this is mis-diagnosed as a strain or sprain. On radiograph, the area is lytic (destructive - eaten away) and productive (bone producing). The lesion often has a sunburst appearance. Before treatment is started it is important to determine if the cancer has spread and a complete workup is necessary to determine the general health of the dog and it's potential ability to withstand treatment. This could include a complete blood count, serum chemistry profile, urinalysis, thoracic, abdominal and expansile radiographs, radiographs of the appendicular skeleton and if possible a nuclear bone scan (not often available). A biopsy obtains a core of bone and is usually done under general anesthesia (a fine needle aspiration can also be used). This sample is examined microscopically to determine the cell type and reach a diagnosis.
Currently, the treatment of choice for OSA is surgery followed by chemotherapy. The goal of treatment is to increase the quality of life and quantity of time and decrease pain. This is achieved through control of the primary tumor as well as prevention of metastasis. Cure is not truly a reasonable goal and is only attained 10% of the time at present. The average length of remission is 1 year (but can be longer). Surgery usually involves amputation of the affected limb. While this may seem drastic, the source of the dog's pain (the tumor) is removed and the dog feels better. Most dogs adapt very well; it is their owners that have trouble with the idea of amputation. Unfortunately, surgery alone does not offer a much longer survival time (4 - 6 months with the dog eventually succumbing to pulmonary metastasis) than no treatment at all (1 - 2 month survival, pet is usually euthanized due to the pain of local progression). Chemo can be used in addition to surgery to try to stop or slow the pulmonary mets. "Limb sparing" or "limb salvage" is surgical option that provides an alternative to amputation. In this procedure, the bone tumor and surrounding tissue is removed and then replaced by healthy bone from a donor and bone grafts from other parts of the dog's body. Most of the function of the leg remains but there is usually a decreased range of motion which will limit the dog's activity. This is an option to consider in dogs that have other orthopedic problems like severe arthritis and wouldn't do well on only 3 legs. There are several restrictions though as to the size and location of tumors that can be treated with this procedure. The best results are with tumors of the distal radius. And limb sparing surgery is always performed in conjunction with chemo. Chemotherapy drugs
do not specifically attack cancer cells but damage and / or kill rapidly
growing cells. This includes cancer cells but also cells lining the stomach
and intestine and the white blood cells. This is why the most common side
effects of chemo are nausea, vomiting, diarrhea and the increased risk
of infection. Hair loss is not common in dogs as it is in people. And,
thankfully, most dogs have no side effects at all! With chemotherapy after
surgery, 50% survive to 1 year and approximately 20% to 2 years. Cisplatin and Carboplatin both contain platinum and therefore are expensive to use. Cisplatin considered to be the "gold standard" in treatment of OSA. It can be effective when used alone or in combination with Adriamycin. Cisplatin may cause kidney toxicity. Carboplatin is a 2nd generation drug and is being reviewed once again, with efficacy questioned. Adriamycin is a potent anti-cancer antibiotic and another choice, either in conjunction with cisplatin or carboplatin. No multiple agent regimen has consistently proven better than single agent to date. Radiation therapy is not effective as a curative treatment for OSA. Usually the tumors are advanced and with the high rate of microscopic spread to other parts of the body, radiation treatment is only considered palliative. It can really reduce pain and improve function. One disadvantage is that it can increase the risk of pathologic fractures (due to the dog using the affected and weakened limb more). Radiation can be combined with chemotherapy to increase survival time.
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