There are things that pet owners can do to reduce the risk of certain types of cancers in their pets. The most common cancer preventive step is spaying or neutering. Spaying young females does, to a large extent, prevent breast cancer. For example, female dogs that are spayed before their first heat (estrus) only rarely develop mammary cancer. Female dogs that have not been spayed have a risk for breast cancer that is 200 times greater than that for dogs that have been spayed before the first heat. Even dogs that were spayed after their first heat cycle are 10 times less likely to get breast cancer than unspayed females. The highest risk of breast cancer in female dogs is for those that are spayed after the fifth heat cycle or are never spayed. For male dogs, the risk of testicular cancer is eliminated with neutering.

While the degree of protection provided to female cats by spaying before the first heat cycle is less well documented than it is with dogs, most veterinarians believe that the risk of breast cancer in cats is also greatly reduced by spaying. The preventive key is doing this surgery before the first heat cycle or as soon after that as possible.

Unfortunately, similar proven steps for preventing other cancers are rare. And, there are some risk factors, such as genetic heritage, that are unavoidable. Even though we know very little about decreasing the risks of cancer, there are some steps pet owners can take to reduce the chance that their pets will develop cancer. Most of these steps involve lifestyle choices.

Good Nutrition and General Care

No diet has been proven to prevent cancer in animals. However, adequate nutrition and good general care not only provide what your pet needs to lead a healthy life, these things will also make it easier for your pet's body to fight cancer and other diseases. For many species of animals, nutritional guidelines have been established through research. Commercial producers of pet foods have used these guidelines to produce well-formulated foods; such products are readily available. Your pet's overall health and quality of life will be enhanced when you provide a diet that is nutritionally appropriate. Learn about your pet's nutritional needs and read pet food labels carefully to be sure the food you are providing meets those needs. This step may also contribute to reducing your pet's risk of cancer.

Reducing Known Risk Factors

Reducing known cancer risks in your pet's environment is a step toward cancer protection that you can take for the member of your family that is often the least able to avoid such risks. For example, by controlling your pet's exposure to sunlight and ultraviolet radiation, you can significantly reduce the risk of skin cancer. The areas on an animal's body that are most likely to develop skin cancer are those with little or no hair or those that do not have pigmentation (color). Therefore, the highest risk areas for skin cancer in cats include the eyelids, the tip of the nose, and the tips of the ears. For dogs, the abdomen is a vulnerable area. Animals with fair or white coloring are more likely to develop skin cancer than animals with dark hair. White or light skin or fur provide less protection from the ultraviolet rays in sunlight.

Owners of animals with white or light coats or skin should protect their pets from direct exposure to sunlight, especially during the hours when ultraviolet radiation is strongest. Ultraviolet rays are strongest during the summer months between the hours of noon and 4:00 p.m. Keeping pets indoors or in well-shaded areas as much as possible during these hours can significantly reduce the risk presented by ultraviolet radiation. Common sense is needed in applying this guideline. Short exposure to sunlight, such as during walks or normal “bathroom breaks,” poses little risk; prolonged exposure, such as that of animals living outside, carries much more risk for skin cancer.

Among humans, smoking and other tobacco usage is a leading cause of cancer. Smoking is not only dangerous for the smoker; it also endangers the health of others exposed to tobacco smoke. This means that anyone living in a home where there is a smoker has an increased risk of health problems, including cancer. Pets that inhale secondhand smoke are more likely to develop cancer and other health problems than animals that live in a smoke-free environment. An owner's decision to stop smoking can, therefore, lower the chances that any pets living in the home will develop cancer.

Prevention and Early Detection

The earlier cancer is detected and diagnosed, the easier it is to treat and the better the outcome of the treatment is likely to be. Even if cancer cannot be avoided completely, early treatment offers the best chance for survival and a return to a normal, healthy life. Routine, thorough physical examination by a veterinarian is the best way for you to prevent fatal or debilitating cancer in your pet.

All animals, especially older animals, should be considered at risk for cancer and receive physical examinations by a veterinarian at least yearly. Exams should include blood and urine tests. These tests can lead to detection of cancer even though the animal may not look, feel, or act ill. Skin maps are used by some veterinarians to track skin masses on pets. These records allow the veterinarian to quickly identify any new masses or unexpected growth of existing masses and test them to determine whether or not such masses are cancerous. This is one method used to catch cancers early when treatment is easier and more likely to result in remission or a cure.

All pet owners should monitor their pet's health regularly. Some signs should alert you to possible cancer. Changes in your pet's body, appetite, and urinary or bowel habits are signs of possible illness. You should also note changes in personality, demeanor, or activity levels. Such changes can happen suddenly or gradually over time. These changes should alert you to have your pet examined by a veterinarian.

Possible Signs of Cancer
Various changes in a pet's behavior or appearance, such as those listed below, might indicate the development of cancer. These are not always signs of cancer; however, paying attention to such changes and bringing them to the attention of your veterinarian as soon as they occur can increase the chance that a cancer will be detected and treated at an early stage. A growing or changing lump Swollen lymph nodes Sudden abdominal swelling Unexplained bleeding from the mouth, nose, or genital area Difficulty when breathing, chewing, swallowing, urinating, or defecating Persistent sores or swelling Unexplained bad breath or other odor Dry cough Lowered stamina Recurrent vomiting or diarrhea Loss of weight or appetite Lack of interest in physical activities Indications of physical discomfort, such as lameness or stiffness

It is crucial to have your pet routinely screened for cancer by a veterinarian. In some cases, veterinarians may use advanced screening technologies such as x‑rays, ultrasonography, magnetic resonance imaging (MRI), computed tomography (CT) scans, and examination of the colon (a colonscopy) to look for cancer. These tools can help your pet's veterinary team detect cancer at an early stage. Screening even when there is no sign of cancer is crucial because—just as with humans—the earlier cancer is detected, the better the treatment outcome is likely to be.

Last full review/revision July 2011