Cancer is the uncontrolled growth of abnormal cells.

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.


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.

If you find an unusual lump or swelling on your pet you should make an appointment for your vet to check it out. Although most lumps are harmless, some can be very dangerous if left untreated.


Most forms of cancer can be treated, but this depends on the type of cancer and whether the disease has spread.

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:

  • Surgical removal
  • Chemotherapy (drug treatment) - Chemotherapy in dogs is used to improve quality of life in pets, and the side effects of chemotherapy seen in people are rarely experienced.
  • Radiotherapy (x-rays)

Quality of life

Discomfort can be severe when the cancer is advanced, but most cancer-related pain can be controlled. Your vet will try to improve your dog's quality of life rather than prolonging the life of your dog if it is suffering.


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 which provide good nutrition even if your dog's appetite is poor.

Life expectancy

The survival chances will depend not only on the type and stage of the disease but also on your dog's general health.

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