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Dog Breed, Weight and Sex May Determine Best Age for Cancer Screening

Four dogs of different breeds sitting next to each other in a wooded area.
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New research using data from over 3,000 dogs has suggested that most dogs should begin cancer screening from age 7, but some dogs, such as large breeds, may benefit from early screening. The study, funded and carried out by the pet liquid biopsy diagnostics company PetDx, is published in the journal PLoS ONE.

Early cancer diagnosis is key

Cancer is the top cause of death among adult dogs. A dog’s chances of developing or dying from cancer vary significantly by its breed – studies suggest that breeds such as Bernese mountain dogs, Irish wolfhounds and flat-coated retrievers have some of the highest rates of death from tumors.

Annual physical checkups and routine blood tests can go some way toward detecting cancers, but often these are not enough to detect the disease early when it is generally at its most treatable.

Less invasive methods for cancer screening, such as liquid biopsies – a technique that looks for tumor markers like cells or DNA in blood samples – have been evolving and developing for use in human patients over the past decade, and the same screening method can also be applied to dogs.

However, no formal guidelines surrounding when this type of cancer screening should be used in dogs currently exist. To tackle this problem, the researchers in the current study investigated the average ages of cancer diagnosis in dogs based on their different characteristics. “Our study provides data to support an evidence-based recommendation for when to start cancer screening in dogs of various breeds and weights,” explained Jill M. Rafalko, lead author of the study and director of scientific communications at PetDx.

Multiple factors at play

The researchers combined data from three cohorts to study a total of 3,452 dogs diagnosed with cancer, grouping them by breed, weight, sex and cancer type.

The analysis showed that the breeds with some of the youngest typical (median) age at cancer diagnosis included mastiffs at five years of age, in addition to Saint Bernards, Great Danes and bulldogs all at six years of age.

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At the other end of the scale, bichon frisés had the oldest median age at 11.5 years, while the combination of “mixed breed” and “other” breed dogs were diagnosed at a median age of 9.5 years. Purebred dogs were, on average, diagnosed at a significantly younger age (8.2 years) compared to the mixed breeds (9.2 years).

The researchers also investigated other factors that could influence the age of dogs’ cancer diagnosis, such as weight, sex and whether they had been neutered. They found that higher weight was linked to younger age at cancer diagnosis, with dogs over 75 kilos diagnosed at a median age of 5 years, compared to a median of 11 years for dogs weighing 2.5–5 kilos.

Male dogs were diagnosed at an earlier age than females (8.3 years compared to 8.7 years) and neutered animals were diagnosed at an older age than intact ones, for both males and females.

Rafalko added, “With this information, we were able to make evidence-based recommendations about the age to start cancer screening in dogs, and the age to start cancer screening in an individual dog, based on their breed or weight.”

“We know that cancer develops over time, and that cancer screening should begin prior to the age of peak incidence – so it is reasonable to start screening for cancer two years before the typical age at which cancer is diagnosed. In short, this means that all dogs should begin cancer screening at age seven, but some large dogs and dogs belonging to breeds that tend to develop cancer at a younger age may benefit from starting screening as early as age four,” Rafalko summarized.

Improving canine cancer diagnostics?

Overall, findings from the study contribute towards establishing potential guidelines for when to start screening for cancer in dogs and inform how characteristics such as breed and weight can influence the onset of cancer.

Nevertheless, Rafalko also elaborated on some of the limitations of the study: “This was a large study involving over 3,000 dogs with cancer. However, certain breeds such as breeds that are less common in the US were not well represented, limiting our ability to provide a recommended age to start cancer screening for these dogs. We would love to be able to add data to this cohort to help better inform screening recommendations, particularly for these underrepresented breeds.”

Reference: Rafalko JM, Kruglyak KM, McCleary-Wheeler AL, Goyal V, Phelps-Dunn A, Wong LK, et al. Age at cancer diagnosis by breed, weight, sex, and cancer type in a cohort of more than 3,000 dogs: Determining the optimal age to initiate cancer screening in canine patients. PLoS ONE. 2023;18(2):e0280795. doi: 10.1371/journal.pone.0280795

Jill M. Rafalko was speaking to Sarah Whelan, Science Writer for Technology Networks.