Cancer Prevention in Pets

By: Dr. Shelby Williams, PharmD, FSVHP and Dr. Joanne Intile, DVM, MS, DACVIM (oncology)

Roger Caras once said “dogs are not our whole lives, but they make our lives whole.” Most would agree that our pets become a part of our family and when they become sick it has a huge impact on us as well. Determining risk factors and cancer prevention has been an area of great research in both human medicine and veterinary medicine. Cancer prevention is an important aspect of any pet’s routine healthcare, and these simple measures can help pet owners and their veterinarians work together to ensure our beloved companions live longer, happier, and healthier lives.

Environmental Exposures
The three biggest culprits include pollution, environmental tobacco smoke (ETS), and pesticides. There is evidence supporting an association between exposure to ETS and lymphoma and nasal tumors in dogs and lymphoma in cats. Exposure to pesticides containing dichlorophenocyacetic acid (2,4-D) is associated with increased risk of lymphoma in dogs, however data is conflicting. See for more information on 2,4-D. Dogs living in urban areas are at increased risk for developing lymphoma.

Cats infected with Feline Leukemia Virus (FeLV) are 60 times more likely to develop lymphoma/leukemia compared with healthy non-infected cats. FeLV infection was the most common cause of blood borne cancers in cats during the 1960-1980s. During that time, approximately two-thirds of cats with lymphoma were co-infected with FeLV. With the development of better screening tests to eradicate or isolate infected cats, as well as commercially available FeLV vaccines, the number of FeLV positive cats decreased dramatically after the late 1980s.

Spaying and Neutering
Hormones can act to promote or inhibit tumor development, depending on the specific cancer in question. Female dogs are less likely to develop mammary tumors when they are spayed early in life, presumably due to lack of exposure of mammary tissue to ovarian derived reproductive hormones. However, neutering may actually increase risk of developing prostate cancer in male dogs, indicating a possible protective effect of hormones in such cases. Neutering may also increase risk of developing osteosarcoma and transitional cell carcinoma of the urinary bladder in dogs, regardless of sex.

Injection Site Sarcomas
The administration of injections (not only vaccinations) can cause injection site sarcomas in cats, but the injection alone is not sufficient to create tumors — more and more evidence points to an inherent susceptibility to tumor development that is “set into motion” in response to the injection. Therefore, injections into a limb instead of near the head or neck are preferred, especially in cats with conditions requiring regular injections.

Regular Physical Exams
One of the simplest preventative measures owners can do is to schedule regular physical exams for their pets every 6 to 12 months. This ensures any changes in status, body weight, etc. are closely monitored and tracked over time and concerns can be addressed as early signs are noted. Any newly noted skin masses should be evaluated as soon as they are noted. It is impossible to determine if a skin mass is benign or malignant based on appearance or feel alone. A fine needle aspirate and/or biopsy should be performed to determine whether further action is necessary.
The treatment for pets diagnosed with osteosarcoma may be amputation, which can be terrifying to hear. TRIPAWDS, whose motto is “it’s better to hop on three legs than limp on four” is a community focused on helping people understand amputation and bone cancer in pets. Here, owners of three-legged pets provide a fantastic support network for each other and owners considering surgery. One can find a group of “peers” to bounce questions off of and read personal experiences on individual blog pages and forums.

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