Cancer is the uncontrolled growth of abnormal cells. The speed of progress and severity of symptoms depends on the type of abnormal tissue cell affected. As many as one in five animals are likely to develop one of the many different forms of cancer at some stage of their lives. The risk increases with age and so, with animals now enjoying a longer life expectancy through improved diets and veterinary care, the number of animals with cancer has been increasing in recent years.
As with human cancers, the causes of cancer in animals, and the processes that occur in the disease, are still not well understood. Possible causes include:
• Toxic chemicals or exposure to harmful radiation.
• Feline Leukaemia Virus (a very common cause in cats).
• Abnormalities in the immune system which usually protects against disease.
• Abnormal genes.
The symptoms of cancer are very variable and depend on the type of abnormal tissue cells involved, the site of the cancer and the stage of the disease. Advanced cases often show weight loss and appetite suppression. Your pet may be depressed, vomit, have diarrhoea or constipation, or fever. Your pet may also get tired easily because of anaemia.
Cancer can occur in any pet at any age but certain types of animals are more susceptible to particular forms of cancer. Animals with white fur and non-pigmented skin, which like to sunbathe, are vulnerable to skin cancers especially on the ears, nose, lips and any other areas where the skin is exposed to direct sunlight. Applying sunscreen may reduce the risk of cancer developing.
Feline Leukaemia Virus is possibly the most common cause of cancer in cats, although not all cats exposed to the virus will develop the disease. Most cats are able to resist the virus but those that cannot will develop permanent infection and three out of 10 of these will get some form of cancer. This virus is not very common in New Zealand, although it does exist.
Cancer can often be treated, but this depends on the type of abnormal tissue cells involved and the stage of the disease. In some cases treatment can produce a complete cure or at least significantly increase the length, or improve the quality of your pet’s life. Sometimes euthanasia is the most humane alternative to avoid unnecessary suffering. There are three basic options for treating cancers. Not all are appropriate for every case and sometimes a combination of treatments has the best chance of success. These are:
• Surgical removal – usually the best choice for most cancers affecting solid tissue. If the cancer is relatively benign or if a more malignant cancer has not yet spread to other parts of the body, surgical removal may often produce very good results.
• Chemotherapy (drug treatment) – the best option for the cancers that affect the blood or multiple areas of the body. It may also prevent or delay the appearance of secondary tumours in other organs after surgical removal of the original lump.
Discomfort in your pet can be severe when the cancer is advanced, but some cancer-related pain can be controlled. Growths are not usually initially painful. Your veterinarian will probably try a gentle painkiller at first and move on to more powerful drugs if this proves ineffective. Your veterinarian will try to improve your pet’s quality of life rather than prolonging the life of your pet if it is suffering.
Attention to your pet’s diet may improve its quality of life. Animals need extra food to cope with the effects of a fast growing tumour but many animals will have a poor appetite and this will accelerate the weight loss. Warming the food or feeding by hand may help stimulate your pet’s appetite. There are also special diets, which provide good nutrition even if your pet’s appetite is poor; e.g. Hills Prescription Neoplasia Diet.
A question that every owner wants answered, but as with human cancer is impossible for your veterinarian to give you an answer with any confidence, is how long will my pet live? The survival period will depend not only on the type and stage of the disease but also on your pet’s general state of health. You should discuss this issue with your veterinarian so that you can decide together on an appropriate treatment plan for your pet. It is understandable that, faced with a diagnosis of cancer, you will feel frightened about the future of your pet – discussing your fears with your veterinarian is the very best way to obtain reassurance and an independent assessment that you are doing what is right for your pet.
© Forrest Hill Vets (2000) Ltd