Imma Perfetto
Cosmos science journalist
Cover your pup’s ears… did you know that the leading cause of death for adult dogs is cancer?
Researchers from an American diagnostics company, PetDx, have developed a blood test to detect cancer in dogs, which they say might lead to earlier intervention.
Currently, canine cancer is generally identified only after clinical signs have developed and existing methods to screen for cancer in dogs, including biopsy, x-rays, and ultrasounds, are more invasive.
In a new study, published in PLOS ONE, PetDx researchers have determined the median age of cancer diagnosis for dogs with different characteristics including breed, weight, and sex. They say the study provides evidence for when to start cancer screening for individual dogs based on their breed or weight.
PetDX suggest all dogs should begin cancer screening using liquid biopsy at age 7, but certain breeds may benefit from screening starting as early as age 4.
Specialist veterinary pathologist, Professor Rachel Allavena, Deputy Head of the School of Veterinary Science at the University of Queensland, who is not affiliated with PetDx, welcomes the idea of blood biopsies for our furry friends – if the technology proves accurate enough.
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“Screening is well established in people to be highly beneficial for both the population and individuals to detect cancer early when it is more easily and effectively treated, so the patient has a better outcome,” Allavena told Cosmos.
“The authors are proposing that this approach would be beneficial for pet dogs.
“Whilst I would sincerely welcome it if it was the case, the major cancers are highly malignant, often difficult, or expensive to treat, and even with best possible treatment will shorten a dog’s life.”
The researchers analysed data on 3,452 dogs diagnosed with cancer in the US, including more than 120 breeds and a wide variety of cancer types, grades, and stages.
Allavena says American dogs are generally comparable to dogs in Australia, though there are differences in the prevalence of some cancers presumably due to different gene pools.
The study determined that the median age at cancer diagnosis for dogs weighing 75 kilograms or more was 5 years, compared to 11 years for dogs weighing 2.5 to 5 kilograms – perhaps unsurprising, given that large breed dogs have a shorter lifespan than small or tiny breeds.
“A large dog like a Great Dane, Wolfhound, Rottweiler might have a typical life expectancy of 8-10 years. I have known many more that die much earlier than this from cancer (2-4 years at diagnosis). Whereas a small breed like a Jack Russell would live to 12-15 years,” says Allavena.
“That cancer is tied to and very common in certain breeds is a well-established phenomenon and something I can confirm as a veterinary pathologist. A lot of this is genetics, some of it will also be biomechanics (this is thought to play a role in bone cancer in large dogs).”
Looking at breeds specifically, the researchers were able to determine that Mastiffs, Saint Bernards, Great Danes, and Bulldogs had the youngest median diagnosis age, at approximately six years.
Irish Wolfhounds, Vizslas, and Bernese Mountain Dogs had median diagnosis ages of 6.1 to 7 years, and, on the other end of the spectrum, the diminutive Bichon Frise had the oldest median diagnosis age at 11.5 years.
Interestingly, according to Allavena, in the study “there are some breeds that seem to develop cancer later despite being reasonably sized dogs, like Beagles.”
The researchers also developed a statistical model to predict the median diagnosis age based on weight – a model that could be applied to breeds with less representation in the study, and to mixed-breed dogs.
They say that their findings suggest the early detection of canine cancer could be improved by beginning liquid biopsy screening two years before a dog reaches the median diagnosis age for their breed or weight.
Would screening make canine cancer treatment more effective or less invasive?
Allavena is cautiously optimistic that, if liquid biopsies for dogs are proven to be both accurate and financially attainable, they could benefit dogs – depending on the treatments available and how early the diseases are detected.
According to a 2022 validation study, the test developed by PetDx, Onkok9, has a sensitivity of 54.7% – meaning it can detect true cancer cases about half of the time – and demonstrated a 98.5% specificity in avoiding detecting false positive cases.
“If we catch them early, are we able to really benefit the dog by intervening at an earlier time point? Is starting chemo sooner going to help? Is doing the surgery early going to help? Because a lot of cancers are very common, really nasty, but they often need very expensive, very complicated therapy,” she says.
For osteosarcoma, early diagnosis may mean limb sparing surgery could be used instead of the more serious full amputation.
But, in the clinically silent hemangiosarcoma – malignant tumours that originate from blood vessels and are often undiagnosed until a dog dies from it – early detection may only result in tumour removal if it spread to an organ that can be surgically removed (like the the spleen, but not the heart).
Ultimately, she says, veterinary oncology is about quality of life over quantity, so it’s not acceptable to make dogs really ill, suffer, or diminish their quality of life by treating them.
“If early detection is going to mean that you have a reduced chemotherapy dose, or less strong treatment, then maybe that is a really important benefit of early detection via liquid biopsy.”