5 Causes of Cancer in Dogs and How to Prevent It

Written and verified by the biologist Samuel Sanchez

Last update: 27 December, 2022

We all know someone who has suffered from cancer, or who has even died from it, and it’s undoubtedly the most common and problematic disease in high-income countries, second only to cerebrovascular conditions. However, do you know the causes of cancer in dogs?

According to studies, the incidence of all types of cancer together in canids is estimated at almost 100 cases per 100,000 dog years. The most common malignancies in Canis lupus familiaris are breast tumors, non-Hodgkin’s lymphomas, and skin cancers. If you want to know more about this group of diseases and their causes, keep reading.

What is cancer in dogs?

Cancer follows the same premise in all vertebrates, be they humans, dogs, cats or whales. As indicated by the National Cancer Institute, this term describes diseases in which there’s a group of abnormal cells that multiply uncontrollably and invade nearby tissues.

This uncontrolled growth of the atypical cell line is due to genetic mutations in its nucleus, which in general disrupt the growth and death rate of the affected cells. By not following the normal patterns of senescence and division, they overgrow and generate a palpable mass, known as a tumor.

However, it should be noted that not all cancers generate tumors (leukemia) and that not all tumors are carcinogenic. When the growth of the tissue mass is self-limited and there’s no risk of migration to other tissues (metastasis), we speak of a benign tumor.

The incidence of benign tumors is 10 times higher in dogs than in cats. Canids are prone to having them.

5 causes of cancer in dogs

In many cases, it’s impossible to find a specific cause of cancer in dogs. This group of pathologies is favored by an amalgam of factors, such as old age, certain previous diseases, the environment, and certain inherited mutations. Next up, we’ll explore the most common triggers.

1. Genetic predisposition

The Golden Retriever breed is the best example that, in some cases, cancer is inherited. Without going any further, 70% of the dogs of this variety end up dying from 2 types of malignant neoplasms: hemangiosarcoma and lymphoma. Genetic studies have shown that certain mutations in the breed’s genome favor the expression of tumors in the long term.

It can be speculated that the higher incidence of cancer in some purebreds is due to the crossing of individuals over time. Reproducing close dogs in the family tree among each other carries this type of risk, since selective breeding sometimes means that they’ll end up establishing very negative pathologies in their offspring.

2. Age

As indicated by the MSD Veterinary Manuals portal, age can play a significant role as one of the causes of cancer in dogs. Up to 50% of dogs older than 10 years are at risk of presenting a malignant tumor, although up to half of the neoplasms are treatable and have a good prognosis.

A decrease in the effectiveness of the immune system could explain part of this trend.

3. Exposure to carcinogens

We all know the harmful effects of tobacco, as it’s easy to recognize that up to 50% of smokers end up dying from their addiction. However, sometimes we forget those non-human passive smokers that inhabit the home, such as dogs and cats.

According to the VCA Hospitals portal, the incidence of nasal tumors in passively smoking dogs increases by 250% compared to those living in healthy environments. They aren’t the only ones, as felines have twice the risk of suffering from lymphomas if their guardians are tobacco users.

4. Hormonal causes

In various animal models, it has been shown that excess circulating estrogen can promote the development of breast cancer. In dogs, for example, the chances that a female will present this type of cancer are 26% if she has gone through 2 different heats. If the dog has been neutered before the first estrus, the probability is reduced to 0.5%.

5. Bad luck or a set of all the aforementioned

Unfortunately, most causes of cancer in dogs remain undiscovered. This pathology is multifactorial and very difficult to explain due to a specific stressor, and therefore, it’s also difficult to prevent it. In any case, it’s estimated that in humans 80-90% of cancers are preventable, since many are linked to tobacco consumption and even an unhealthy lifestyle.

Although dogs don’t directly consume cigarettes or drink alcohol, they can be exposed to carcinogens unintentionally, such as tobacco smoke, insecticides, toxic compounds and many other harmful elements. Furthermore, obesity and a sedentary lifestyle can be expected to promote the development of neoplasms, just as it does in humans.

How to avoid the development of cancer in dogs?

Sources already cited estimate that 1 in 4 dogs will have cancer at some point in their life, and this percentage increases to 50% if they are over 10 years of age. Although sometimes this highly conflictive disease group arrives unannounced, there are a few things we can do to minimize the risk. Among them, we highlight the following:

1. Sterilization: Sterilization has been shown to be an effective method of reducing the risk of breast cancer in females and testicular cancer in males, among many other conditions.
2. Deworming: In animal models, it has been shown that constant inflammation of a tissue promotes the appearance of cancer. Therefore, avoiding parasites, bacteria and viruses that can damage organs in the long term is essential in order to minimize the risk of neoplasms.
3. Healthy environment: Not smoking in the same room as the pet is essential in order to prevent pets from developing oropharyngeal, lung or nasal cancers in the long term.
4. Avoid stress: Long-term stress suppresses the immune system, which favors the appearance of diseases. Your dog needs to feel comfortable at all times.

Of course, the most important recommendation is to visit the vet regularly and take your dog to the clinic as soon as you notice something strange. The causes of cancer in dogs are difficult to find in many cases, but if vets detect tumor masses early, the prognosis is always more positive.