Cancer

An Overview

Cancer is a disease of aging dogs, and now that dogs are living longer because of thriving care, the prevalence of cancer in dogs has increased. Now, this isn’t to say every senior dog will develop cancer, but the aging body isn’t the same; and simply due to being alive longer, older dogs accumulate more mutations into their cells’ DNA and have had more exposures to potential carcinogens than younger dogs. In addition, aging individuals progressively lose the fitness and the associated defenses against cancer that are present in young individuals.

Although cancer is often discussed as one disease, it is important to note this term actually describes more than 100 diseases with different characteristics, and with unique patterns of behavior. So, while you will find many textbooks on the subject, cancer does not play by “the rules.” There are many varieties of cancers stemming from different cell lineages within the body. As you may venture to guess, this makes cancer difficult to detect, because it starts from something microscopic (you can’t see it with the naked eye). It also makes cancer difficult to treat, because cancer is a growing thing capable of change just like any other cell or tissue.

Dog owners often ask, are there tests available to detect cancer early?

The answer to this question is nuanced. Many people choose to have imaging including radiographs, ultrasound, or “CT” (computed tomography, an advanced form of imaging) performed on their dogs every 3 to 6 months to assess abnormalities in organs commonly affected by metastatic cancers. This practice is relatively benign. The risks from radiation exposure are probably minimal. And there is a small chance of detecting a tumor. However, if the tumor is visible, the detection is no longer “early.” It just means it was found before it caused systemic issues. In our experience, this practice does not change the outcome of the dogs meaningfully and it is not sensitive or specific enough for us to recommend it routinely.

There are relatively new “liquid biopsy” tests in the market and there is a tremendous marketing push for these tests to be used for early detection. However, it is very important to recognize that neither the NuQ test nor the OncoK9 test are validated for early detection, so the likelihood that they can detect the disease at an early stage is not known, nor is their capacity to differentiate early cancerous forms from any other condition. And maybe more importantly, neither test provides an opportunity to take action that would alter the change in the course of the disease. The recommendations after a positive result on a liquid biopsy test are to then do imaging, which has the same limitations as doing imaging by itself, except with the added cost of the test. At this point, there is not sufficient evidence of benefit to recommend these tests as routine screening tools for early cancer detection.

Quality of Life

Minimizing the effect cancer has on our lives as well as our four-legged friends is a shared goal. That begs the question of, what other options do we have? While alternative therapies and supplements might have some benefit, they are ineffective to treat and/or prevent cancers and should never replace conventional treatments recommended by a qualified veterinarian. Experimental therapies offered at academic veterinary teaching hospitals or private specialty hospitals provide reasonable options for some dogs, and participation in these legitimate, controlled trials is one way to help advance knowledge and develop more effective treatments.

You are encouraged to take a look at the following sections that dive further into the world of cancer, investigating some of the most common types seen in man’s best friend.

Common Canine Cancers

Read about the common canine cancers that often affect Portuguese Water Dogs.

Hemangiosarcoma
Mast Cell Tumor
Lymphoma

This article has been written by Meagan Wojtysiak, Kelly Makielski, DVM, MS, DACVIM (Small Animal Internal Medicine) Animal Cancer Care and Research Program, University of Minnesota, St. Paul, MN