Cancer Diversity in Cats and Dogs
Each month we select one dog and one cat to be our "Oncology Pet of the Month." We write a small summary of their case and provide information on their diagnosis and outcome. Their stories are displayed in both of our exam rooms: one for the cat and one for the dog.
We also publish the information on our hospital’s Facebook page and mail a copy of the summaries to the owners. It’s a great way to disseminate information about veterinary oncology, provides reading material for owners while they wait for their pets to finish their treatments, and it’s also a pretty darn cute thing to do.
Picking a "Dog of the Month" is usually fairly easy — we have a steady caseload of canines undergoing chemotherapy that are doing well or have completed treatments and are living their lives cancer-free several months to even years after their diagnoses. We also have a bigger representation of a variety of tumor types in our dog patients, so redundancy of information from month to month isn’t a problem.
Selecting a cat is much more difficult; not because we don’t have a great pool of candidates to pick from, but because we seem to have a much more limited number of feline patients that have positive outcomes with much less diversity in their diagnoses.
The struggle had me wondering what could be a reason for the differences between the two species when it comes to cancer. Experience affords me the ability to suggest some theories, but I’m not sure I’ll ever be able to truly explain the uniqueness of cats.
On a very basic level, one limitation could be because I see fewer cats than dogs on a weekly basis. I’m not sure if it’s because dogs are more popular where I practice, as it’s well known how geography definitely dictates demographics of caseload for veterinarians. I have colleagues who practice in larger metropolitan settings who see 90 percent felines simply because cats are easier to keep in high rise buildings, and when I worked in upstate New York, in a region close to large dairy farms and large scale properties, I saw 90 percent canines.
Where I work now, I probably see one new feline cancer case for every 3-4 new canine cases, so even though the numbers are slightly better, they are still low compared to dogs.
In general, animals will mask signs of sickness as part of a defense mechanism for survival. This, coupled with an animal’s lack of ability to communicate feelings and emotions in ways we can readily understand and interpret, limits our ability to detect illness in early stages.
Cats seem particularly adept at behaving completely normally while simultaneously bearing large disease burdens, until they reach a tipping point, from which a rapid decline in health status is typically inevitable. This means that cats are often first diagnosed with cancer with 1) widespread disease and 2) advanced clinical signs. Both can severely limit therapeutic options and success rates of treatments.
We are also somewhat restricted in our chemotherapeutic options for cats. Several drugs we can use in dogs cannot be used in cats because of potentially fatal side effects. We have a handful of first-line chemotherapeutics available in our arsenal, but when these drugs are rendered ineffective, or if the cat should not tolerate them, we have far fewer choices to move on to. This, coupled with the fact that cats are often presented to me with advanced disease, often means a poorer outcome in the long run.
Although the risk of a severe side effect from chemotherapy is very low, it’s not uncommon for cats undergoing treatment to experience issues with poor appetite and weight loss. These are not life-threatening complications, but I do think they can be emotionally taxing and frustrating for owners. Nausea and inappetance can be treated medically, but the most effective way to do so is with oral medications. Administering pills to healthy cats can be challenging; administering those same medications to cats that aren’t eating well and are smart enough to know their owners are about to try to give them a pill can be downright impossible.
Fortunately, medications can be made into liquids, which many owners find easier to give, or even creams that can be applied to the inside of the cats’ ears. These compounded medications can ease stress and strain for both parties.
Aside from the perils of medicating their cats, many owners also find it a struggle to simply capture their cats for their treatments. Dogs are often much easier to convince (aka trick) to go on weekly car rides to the vet. This, coupled with the above-mentioned problems, creates a completely different emotional atmosphere for cat owners that may affect their decision to continue treatment, or to pursue alternative treatments when the front line therapy isn’t working. There is conflict between wanting to help their cat, while simultaneously feeling as if they are in some way altering their bond with their cat.
We are taught in veterinary school that "cats are not small dogs," and this adage never holds truer than when dealing with cats and cancer. Don’t get me wrong. I love my frustrating feline patients and I’ve often said there’s no such thing as a crazy cat person; there are just people who like cats as much as I do, and then there’s everyone else.
I think my observations just indicate a need for greater cat-specific cancer research, and I would urge cat owners to schedule regular checkups with their veterinarians — and discuss what kinds of testing they recommend as part of an early cancer detection plan.
And on my end, I’ll keep on treating these feisty felines, because we need our steady supply of "Cats of the Month."
Dr. Joanne Intile