This expert response comes from David Vail, a veterinary oncologist and Barbara A. Suran Chair in Comparative Oncology at the UW School of Veterinary Medicine.
Question: Three of the four dogs I’ve owned have had cancer (one twice). Is it known how many deaths of dogs in the U.S. are caused by cancer, which kinds of cancer are the most prevalent, and why? —Margie
Answer: I certainly sympathize with your experience with cancer in your companion dogs. I have lost many of my dogs over the years to cancer. This is not unexpected as the number one cause of death (mortality) and morbidity (illness) in dogs over six years of age is cancer — roughly 60 percent.
This is partly due to the good care you provide your companions (cancer increases with age) through good nutrition, vaccination, and preventative healthcare. Additionally, dogs do not suffer from atherosclerotic heart disease like people. If you remove heart disease from the equation, cancer also becomes the number one cause of death in people. So, it is nothing we, as caregivers, do wrong. Rather, the natural aging process results in increased cancer incidence.
The most common cancers in dogs are skin cancer, cancer of white blood cells (lymphoma), and cancers of connective tissue (called sarcomas). The most common types of sarcoma are soft tissue sarcomas, osteosarcoma (bone cancer), and hemangiosarcoma (sarcoma of blood vessels, usually in the spleen).
There are many factors involved in ultimately causing cancer. Dogs are now living longer to an age where cancer incidence increases. The longer a dog or person lives, the more chance for cancer-causing mutations in our DNA to build up. Additionally, as we age, our immune system (designed to recognize and kill abnormal cells before they become cancer) also ages, becomes “tired,” and fails to recognize these abnormal cells.
Genetics and environmental factors — some known and many currently unknown — also come into play. We at UW are working towards a better understanding of cancer and ways to prevent and treat cancer in companion animals and people. To learn more, visit uwveterinarycare.wisc.edu/oncology.
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