Cancer in companion animals is a leading cause of death. The prevalence of cancer is increasing and a number of factors are contributing to this increase, in part reflecting the ageing of our canine and feline populations (Cooley et al 2003, Lord et al 2007). Cancer is predominantly a disease of middle aged to older patients, and as our ability to control other diseases, improve nutrition and practise good preventative medicine has resulted in our companion animals living longer, then it stands to reason that the incidence of cancer will also increase.

It is important because, to many individuals, the dog or cat with whom they share their home and lives is an integral member of the family and whatever decision they ultimately make as to treatment is made with the best intentions for the animal in question. It is our responsibility as medical professionals to provide the facts and the options to our clients so that they can make an informed choice.

As medical professionals it is our responsibility to provide the best care for our veterinary patients in respect to cancer diagnosis and treatment and in doing so acknowledge the strength of the human–animal bond. The recognition of the importance of companion animals to the emotional wellbeing of human beings is now well known – not only do they ‘complete the family’ and provide valuable lessons to children about the responsibility of relationships, they provide companionship and in some cases a valuable link to the outside world when they help us as guide dogs, hearing dogs, dogs trained to assist the disabled, in Search and Rescue and many other fields. Dogs have been shown to improve quality of life and reduce stress, and studies have shown that people living alone with a dog or cat for a companion have a better quality of life than those without. These significant benefits to our lives mean that the relationship people have with an animal may be of greater or equal importance to them as their relationships with other people. Clients who have invested a great deal of love and care into an individual do not find it acceptable to be told, ‘Your dog/cat has cancer and should be put to sleep’. They do not consider the individual as a disposable item easy to replace, but rather want to know what can be done to help the dog/cat standing before you.

Prevention is better than cure. In the field of human oncology we encounter a great deal of information on preventing cancer and the role that life-style choices contribute to its development (Soerjomataram et al 2007). We are all aware that smoking is linked to lung cancer, excessive exposure to sunlight with melanoma and Western ‘high-fat’ diets with breast and colon cancer. In turn, the incidence of many cancers can be prevented in our veterinary patients. Early ovariohysterectomy not only eliminates neoplasia of the uterus and ovaries, it also significantly reduces the incidence of mammary carcinoma. Neutering males eliminates testicular cancer. Counselling clients on neutering early is an easy and important part of preventative medicine.

Early diagnosis improves prognosis in many instances. In human oncology screening tests are available for the more commonly seen cancers, mammograms for breast cancer, cervical smears for cervical cancer, etc. We can apply this principle easily to our veterinary patients without incurring huge costs. The simplest and often the most effective test is a good physical examination to include a rectal exam. Routine rectal examination on dogs of greater than 5 years of age would allow for early detection of canine anal sac adenocarcinoma, thus reducing the need for extensive surgery and improving potential outcome for the patient. It also allows for early detection of prostatic neoplasia, particularly in neutered dogs.

Many cancers in veterinary oncology are detected only when they are very advanced. Part of this is because our patients cannot tell us when something just isn’t right, but also because they will carry on appearing relatively normal to the client but just ‘slowing down’. Many cancers are occult and it may be some time before an obvious abnormality becomes apparent. Offering good diagnostic evaluations early will improve prompt detection of cancer and the opportunity to treat patients early; this in itself will improve survival times for many patients. The veterinary surgeon needs to be constantly thinking about underlying causes for the simplest of presenting signs: