Cancer in Dogs: Breed & Size Matter, Study Shows

If your dog is bigger, male and a purebred, it may get a diagnosis of cancer earlier in its life compared to other dogs, a new study finds.

A dog’s size, gender and breed appear to affect its average age at cancer diagnosis, researchers found. This should inform canine cancer screening guidelines, they wrote in the Feb. 1 issue of PLOS ONE.

Cancer kills more adult dogs than any other cause. Detecting it early can provide better treatment options, just like with humans, the authors said in background notes.

Although new noninvasive blood tests for dogs can detect tumor DNA long before other signs of cancer arise, the authors say no formal guidelines exist for when dogs should be screened.

Co-author Jill Rafalko of PetDx in La Jolla, Calif., and colleagues set out to change that.

“Dogs now have a new option for cancer screening called ‘liquid biopsy,’ which, similar to the human version of this test, leverages next-generation sequencing technology to detect multiple types of cancer using a simple blood draw,” Rafalko and her colleagues said in a journal news release.

“However, the age to start screening for cancer in dogs can vary depending on their breed or weight. Our study, involving over 3,000 cancer-diagnosed dogs, found that all dogs should begin cancer screening at age 7, but certain breeds may benefit from screening starting as early as age 4,” the authors said.

The researchers’ first step was to determine the median age at cancer diagnosis of dogs with different characteristics.

They analyzed more than 3,400 dogs with cancer in the United States, finding that giant breeds like mastiffs, males and purebred dogs tended to be diagnosed with cancer at younger ages.

The median age at cancer diagnosis for dogs weighing roughly 165 pounds or more was 5 years, meaning half were diagnosed at a later age and half at a younger age. That compared to 11 years for dogs weighing roughly 5.5 to 11 pounds, they found.

The mean diagnosis age for purebred dogs was 8.2 years, compared to 9.2 years for dogs whose breed was described as mixed or “other.”

The researchers determined that mastiffs, Saint Bernards, Great Danes and bulldogs had the youngest median diagnosis age, about 6 years old. Irish wolfhounds, vizslas and Bernese mountain dogs had median diagnosis ages of 6.1 to 7 years. At 11.5 years, the bichon frise had the oldest median diagnosis age.

Female dogs were typically diagnosed with cancer at older ages than males. Neutered dogs were diagnosed later than intact dogs.

The researchers proposed that blood tests should begin two years before a dog reaches the median diagnosis age for its breed or weight.

More information

The U.S. Food and Drug Administration has more on dogs and cancer.

SOURCE: PLOS ONE, news release, Feb. 1, 2023

Source: HealthDay