Animal Cancer Update - Canine Osteosarcoma

Osteosarcoma is the most common bone cancer in dogs. It most often occurs in a front leg away from the elbow, or a back leg close to a joint. It can also occur in bones of the spine or the skull. Because this is a serious disease that is rapidly fatal without correct treatment, your veterinarian will want to get a certain diagnosis very quickly. This can be done by taking a biopsy, and having a laboratory examine the sample. In some cases, the lesion is so aggressive that limb amputation may be necessary immediately – the sample is then taken at the time of surgery and submitted. Although the surgery required to remove an osteosarcoma is aggressive, you must realise that this is the most effective form of pain control for the condition. Most dogs do very well after surgery, and are typically more comfortable within a few days of surgery than they were before. Dogs generally will not show symptoms of chronic pain – by the time it is severe enough to notice, for example by decreased appetite, the dog has suffered enormous discomfort.

Chest x-rays are often taken prior to surgery. If the tumour can be seen in the chest (about a 10% chance), then treatment aims to restore quality of life for up to a year . If there is no tumour visible in the chest, this means that the cancer is not advanced (but will almost certainly be hiding there) and that cancer treatment has a greater likelihood of achieving long term control. Unfortunately, if surgery is the only treatment, most dogs will not live more than 3 or 4 months. With cancer therapy, about half of dogs will live 16 months or more, and about 1 in 5 will be cured. Cancer therapy therefore obtains good control of the disease and importantly in most dogs causes no side effects: 70% of the time our treatments have no side effects at all, and another 25% produce only brief, mild problems. Only one dog in 20 will have a serious reaction to the medication, which is almost always successfully and rapidly controlled.

Because of the nature of the drugs used to treat osteosarcoma, you should be referred to a veterinary oncologist.

Thanks to new medications, dogs with biopsy-proven osteosarcoma can now have effective treatment WITHOUT needing surgery. Medical-only treatment is not as reliable or as durable as standard treatment (surgery plus medication) and therefore should only be used in circumstances where the patient is not expected to cope with amputation (due to severe arthritis in other limbs, for example). It employs a combination of chemotherapy and either a new bone drug called pamidronate or radiation.

Costs can be very high with these sorts of treatment. Surgery may cost up to several thousand dollars, and medical cancer treatments can cost the same again. The cancer therapy is given via a drip, every 2 to 3 weeks on up to 6 occasions, and does not require overnight hospitalisation. It is important to remember that all the treatment for this disease is designed to restore quality of life, and to then provide as much time as possible. Quality of life is the primary objective.