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Pet Owner Version

Reducing the Risk of Cancer


Manuals Staff

Reviewed/Revised May 2020 | Modified Nov 2022
Topic Resources

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. There is scientific evidence about the risks and benefits of these procedures for both cats and dogs. In both species, sterilization will reduce the risk of developing mammary cancer in females and testicular cancers in males, but timing of sterilization for reduction of risk varies.

There is evidence that spaying cats before the first heat cycle (which may occur as early as 4 months of age) will substantially reduce the risk of mammary cancer. This is important because most cat mammary tumors are aggressive malignant cancers, and surgery (even a radical mastectomy) rarely results in a cure. Also, studies have shown that there do not seem to be any adverse health consequences to sterilizing cats as early as 6-14 weeks of age. The neutering of male cats is commonly used to modify behavior and make them better pets; testicular tumors are benign, and they are not common.

For dogs, the situation is not as clear cut. Breed predispositions for certain cancers, orthopedic problems, and other potential health problems should be taken into account when planning whether and when to spay and neuter dogs. The spaying of female dogs before their first heat cycle is most protective against developing mammary tumors, about half of which will be malignant cancers. There may be some benefits to delaying spaying or neutering in dogs until the growth plates of the leg bones have closed. Each dog and pet owner's situation and goals should be evaluated with a veterinarian to determine the timing for spaying and neutering.

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.

Obesity in pets is an increasing problem in the US and has been associated with a myriad of health problems. Cancer is not the most common problem associated with obesity, but it is an avoidable problem. Your veterinarian can teach you how to assess your pet's body condition so that you can adjust the amount of food given for optimal health.

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 family members that are 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 pmin many northern hemisphere locations. 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, creates 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 (called secondhand smoke). This means that anyone living in a home with 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.

There may be toxins in a home environment (such as pesticides and herbicides) that are known carcinogens. Safe storage of all chemicals and household products is recommended to avoid accidental exposure.

Vaccines can be beneficial but in some cases may increase the risk of cancer. For example, feline leukemia virus causes cancer in cats, but now that we have a vaccine against the virus, this is preventable, especially if you keep your cat indoors and away from cats potentially infected with the virus. On the other hand, some vaccines have been associated with cancer development. The most well known is the development of sarcomas at vaccination sites. Since this was discovered, changes to vaccination schedules (recommending fewer vaccinations at longer time intervals) and new formulations by vaccine manufacturers are helping to reduce this risk.

Early Detection

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

The earlier cancer is detected and diagnosed, the easier it may be 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 that may be benign or malignant growths on pets. These records allow the veterinarian to quickly identify new masses, or unexpected growth of existing masses, and take a sample to determine whether such masses are cancerous. Sampling skin masses is easily done by a veterinarian inserting a needle into the mass and removing some cells. The cells are then spread onto a glass slide, stained, and examined under a microscope. The slide may be sent to a veterinary pathologist to review the types of cells and determine whether the mass is more likely benign or malignant. 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.

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 colonoscopy) 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.

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