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Wednesday, May 25, 2022

Cancer in dogs and cats

Carlos Coto
El Dr. Carlos Coto, es egresado de la escuela de veterinaria ESFA (Universidad Veritas) en el 2011, desde entonces se ha dedicado a la medicina interna de animales de compañía, y desde 2013 con completo énfasis en oncología clínica. / Dr. Carlos Coto graduated from the ESFA veterinary school (Universidad Veritas) in 2011. He has practiced internal medicine for companion animals ever since, and, since 2013, has focused exclusively on clinical oncology.

“Doctor, is there any way you could have prevented this disease in my pet?” That’s one of the most frequently asked questions when I consult with the owner of an animal that has been diagnosed with cancer. Most of the time, my answer is no. The explanation has to do with what causes this disease in these animals.

Incidence of cancer is extremely high in dogs. It’s slightly lower in cats, but still fairly high.

Cancer results from damage to the animal’s DNA, which alters the genetic code, causing cells to replicate in an uncontrolled manner. These cells manage to avoid all the mechanisms that could normally detect and eliminate DNA damage. The mutations also allow new blood vessels to form in order to irrigate and bring nutrients to these cancer cells, and create processes that allow it to spread locally through the invasion of surrounding tissues or spread to other distant sites in the body (metastasis).

Vitalvet patient receiving treatment. Courtesy Carlos Coto / El Colectivo 506
Added to this—thanks to advances in medicine in the treatment and prevention of other diseases, the development of vaccines that prevent some fatal diseases, and complete and balanced diets—our pets live much longer than before. As a result, all of this DNA damage or mutations accumulate over time, increasing the chances of developing cancer as our pets age. Of course, young patients can get cancer, too.

Despite all of this, we do have some options to reduce the incidence of some of these diseases. It has been determined that spaying females can significantly reduce the incidence of breast cancer; it also eliminates the probability of tumors in the ovaries or uterus. In males, castration prevents the development of testicular tumors. It is estimated that 90% of non-neutered males will have a testicular tumor after 10 years of age.

What’s more, in dogs, there is a disease known as canine transmissible venereal tumor (TVT). As its name implies, is the only tumor that can be transmitted through sexual contact. This tumor can cause tumors, primarily on the reproductive organs. Therefore, castration avoids this risk.

A few studies seem to suggest that early castration in dogs over 20 kilos (about 44 pounds) could increase the incidence of cancer, as well as some orthopedic problems. This is why dogs over 20 kilos should not be castrated in their first year of life. Females should be spayed after their first heat and before their third.

In cats, two of the primary infectious diseases—FeLV (feline leukemia virus) and FIV (feline immunodeficiency virus)—have been shown to greatly increase the incidence of cancer, primarily leukemia, or cancer of the blood, and lymphoma, cancer of the lymphatic system. This is why it is extremely important when adopting or buying a cat to find out whether it is a carrier of any of these diseases.

In tropical countries like ours with significant sun radiation, we know that measures must be taken in both dogs and cats to reduce exposure to the heaviest hours of sunlight. The use of sunscreen or clothing with UV protection is also recommended, mostly for animals with white skin and hairless areas such as the abdominal area and inner thighs in dogs—and in cats, their nose, forehead and ears. Such exposure increases the incidence of some skin tumors such as squamous cell carcinoma and cutaneous hemangiosarcoma.

If you plan to buy a dog or cat of a specific breed, you should do some research beforehand: some breeds have a higher incidence of cancer. An example is the Golden Retriever. That’s why the ongoing Golden Retriever Lifetime Study will study 3,000 Goldens throughout their lives to evaluate genetic, environmental and nutritional risk factors. It’s the largest study ever done, and we hope that in a few years it will provide many more answers as to why this breed is so susceptible to cancer, and help us find new options for prevention and treatment.

Vitalvet patient receiving treatment. Courtesy Carlos Coto / El Colectivo 506
Exposure to factors such as tobacco smoke has also been associated with a higher incidence of cancer, so if there are smokers at home, they should smoke outside and away from pets. Exposure to some environmental factors such as insecticides and pesticides have also been associated with a higher risk of suffering from this disease.

One of the most discussed issues today in terms of cancer prevention is the diet of our pets. For example, some argue that commercial diets, whether grain or canned, increase the incidence of cancer due to the poor quality of the raw materials or the use of preservatives. However, the reality is that there is no scientific evidence for this.

There is talk that “BARF” diets (bones and raw food) or home cooked diets can reduce the incidence of the disease. This claim also lacks scientific evidence. The few studies that have been done to try to prove this have large biases. The long-term effect of such diets, beyond some improvements in gut flora and digestion for some individuals, is also unknown. If, as an owner, you decide to employ any of these diets, it is imperative that they are formulated by a specialist veterinarian or nutrition professional. That person can help you avoid any nutritional deficiencies or cross-contamination when handling raw food, since these can cause health problems in the short, medium and long term in pets.

It’s been shown that obesity in people increases the risk of breast, uterine and liver cancer. In pets, both canine and feline, we know that obesity increases the risk of suffering from orthopedic problems, diabetes, and respiratory problems, among others that secondarily affect the longevity of our pets. Obesity is also associated with a higher risk of cancer, but without strong scientific evidence to support it. It’s probably a matter of time before more significant studies tell us more about this relationship, but in short: obesity affects the health of our pets and should be avoided as much as possible.

Another topic that has been widely discussed by veterinary nutrition specialists in other latitudes is the consumption of carbohydrates. There are groups that suggest that low carbohydrate diets (less than 20%) can prevent cancer and even its progression when it has already been diagnosed. The reality is that there are no studies to support these claims either, and the few that have been conducted lack reliability. From a more physiological point of view, the body of a healthy adult animal is capable of producing glucose—the carbohydrate from which tumor cells, as well as those of the rest of our body, obtain energy—from other substances. These include the glycogen that we store in our muscles, the fatty acids and amino acids obtained from the consumption of fats and proteins, and the liver. All of those produce glucose to help the body function, even when carbohydrate consumption is restricted. This is not an invitation to give carbohydrates freely to our pets; however, know that the ideal is for our pets to consume balanced diets that keep them at an ideal weight.

The care of pets through proper veterinary control, and reduced exposure to the associated factors I’ve mentioned, can reduce pets’ cancer risk. A balanced diet is another strategy that can reduce the risk. Of course, we must not forget the existence of unavoidable genetic and environmental risk factors, and that there is no single remedy that prevents or cures malignant diseases. Cancer is a spontaneous, random, and multifactorial disease. In the end, early diagnosis is the best tool we have—not to prevent cancer, but certainly to try to cure it.

Support for this story was provided by Instinct, a dog and cat food produced in the United States and imported to Costa Rica since 2014 by PROVETCRE, a MyPYME that cares about Costa Rican pets and what they eat. Instinct’s mission is to transform the lives of pets: “We believe that all pets deserve the best life possible. And if you ask us — it starts with food.”
This week, Dr. Coto, founder and specialist at Vitalvet, shares his knowledge through this column.
You can find Instinct in every province of Costa Rica. Find your closest point of sale on Instagram, @Instinct.CostaRica
Follow the brand in Costa Rica on Facebook at @Instinct.CostaRica.
If you are a veterinarian interested in providing Instinct as an option for customers, call PROVETCRE at 2215-4399.

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