There are more than 200 forms of cancer and many appear to have genetic components. Most occur later in life. Facetiously, but truthfully, the best way for a pet to avoid cancer is to choose its parents carefully. Avoid exposure to known carcinogenic agents. Never feed mouldy food. Some moulds are carcinogenic. Feed a balanced diet with ingredients known to support the immune system. Avoid any food additives known to be carcinogenic in other animals. Don't let your cat or dog get fat. Fat promotes certain cancers including breast cancer. Inactive people are almost twice as likely to develop cancer as those who exercise regularly. The same may apply to pets. Give your dog regular exercise. Avoid excess exposure to direct sunlight in light coated cats and dogs. Groom and physically examine your pet routinely for lumps and bumps.