Cancer is the uncontrolled growth of abnormal cells. The speed with which a cancer spreads and the severity of the disease it causes depends on the type of tissue cell affected. As many as one in five dogs are likely to develop one of the many different forms of cancer at some stage of their lives. The risk of developing cancer increases with age. This means that, as dogs now enjoy a longer life expectancy through improved veterinary care, the number of animals with cancer has been increasing in recent years.
As with human cancers, the causes of cancer in dogs are still not well understood. Possible causes include:
- Toxic chemicals or exposure to harmful radiation.
- Abnormalities in the immune system that usually protects against infectious diseases.
- Abnormal genes.
The signs of cancer are very variable and depend on the type of tissue cells involved, the site of the cancer and the stage of the disease. Animals with advanced cancers often show weight loss and loss of appetite. If your dog has cancer it may be depressed, vomit, have diarrhoea or constipation or fever. Your dog may also get tired easily because of other effects caused by the cancer, e.g. anaemia. Cancer can occur in any animal and at any age, but certain types of dog are more likely to get certain forms of cancer.
Yes, most forms of cancer can be treated, but this depends on the type of cancer involved and whether the disease has spread. The outcome of treatment can be very variable. In some cases treatment can produce a complete cure, or at least significantly increase the length or improve the quality of your dog’s life. Sometimes euthanasia is the only humane alternative to a slow and painful death.
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. The treatment options are:
Usually the best choice for most cancers of 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 often produces very good results.
Chemotherapy (drug treatment)
Chemotherapy is the best option for cancers affecting the blood or multiple areas of the body. Drug treatment may also prevent or delay the appearance of secondary tumours in other organs after surgical removal of the original lump. Chemotherapy is used to improve quality of life in pets and the side-effects of chemotherapy seen in people are usually not seen in dogs.
Radiotherapy is often effective when tests have clearly shown the extent and size of the tumour. The radiation is usually delivered by a special machine in a radiotherapy unit. A beam of radiation is most effective on cancers of the extremities (such as the limbs and head) where it is less likely to damage normal tissue before reaching the tumour.
Radiotherapy units are only located in a few specialised centres and your vet would need to refer you to a cancer specialist for this form of treatment. In some cases it may be possible to treat the cancer by injecting radioactive material into the body.
Discomfort can be severe when the cancer is advanced but most cancer-related pain can be controlled. Your vet will probably try a gentle painkiller at first and move on to more powerful drugs if these are required. Your vet will try to improve your dog’s quality of life rather than prolonging the life of your dog if it is suffering.
Careful attention to your dog’s diet may improve its quality of life. Dogs need extra food to cope with the effects of a fast growing tumour but many cancer patients have a poor appetite and so lose weight. Warming the food or feeding by hand may help stimulate your dog to eat. There are also special diets designed for animals with cancer that provide good nutrition even if your dog’s appetite is poor.
This is the question that every owner wants answered but, as with human cancer, it is impossible for your vet to give you an answer with any confidence. The survival chances will depend not only on the type and stage of the disease but also on your dog’s general state of health. You should discuss this issue with your own vet so that you can agree between you an appropriate treatment plan for your dog.
It is understandable that, faced with a diagnosis of cancer, you will feel frightened about the future for your pet. Discussing your fears with your vet is the very best way to obtain reassurance and an independent assessment that you are doing what is right for your pet.