Size, sex and breed can predict cancer diagnosis in dogs

cancer is common in dogs. About one in four will develop cancer at some point in their lifetime, and this proportion rises to around 50% after a dog reaches their 10th birthday. A new analysis of thousands of dogs reveals that characteristics such as size, breed and whether an animal has been repaired are associated with how quickly our furry friends might be diagnosed with the disease.

Researchers have looked at the age of cancer diagnosis in dogs in the past, but these studies have mostly focused on specific breeds or kind of cancer. Some have been carried out in Europewhere common breeds, as well as other factors such as neutering or neutering practices, differ from those in the United States, says veterinary oncologist Andi Floryco-founder and chief medical officer PetDx, a California-based pet diagnostics company. “We really wanted to develop something that was applicable to the population of dogs we have here. [in the U.S.],” she says.

To determine which factors were associated with age of cancer diagnosis, Flory and her team at PetDx evaluated previously collected data from 3,452 dogs in three separate groups. Two of these sample groups were from university sites in the United States: one from the University of California, Davis, and the other from a consortium including Colorado State University, the University of Ohio State, University of Wisconsin-Madison and others. Samples from the third cohort were collected in an earlier study by PetDx, which was carried out at 41 different sites in several countries, including the United States, Canada and Brazil.

The researchers found that, overall, the median age of dogs at cancer diagnosis was 8.8 years. Men were diagnosed at a younger median age than women (8.4 versus nine years). And neutered and spayed dogs were spotted later than unfixed ones (8.9 versus 7.9 years in males and nine versus 7.3 years in females). The team also found that purebred dogs tended to be detected at a younger median age than mixed-breed dogs (eight vs. 9.5 years) and that larger size was associated with more diagnosis. early. Dog breeds with the youngest median age of cancer diagnosis (seven years or younger) included Mastiffs, St. Bernards, Great Danes and Bulldogs. Those on the other end of the spectrum included Bichon Frizes, West Highland White Terriers and American Staffordshire Terriers, all of which had a median age of diagnosis of 10.5 years or older. The results were published this week in PLOS ONE.

“I’m glad to see more larger scale studies like this in veterinary medicine, because not so long ago we really didn’t have this kind of research,” says Lisa Moses, veterinarian and bioethicist at Harvard Medical School, who was not involved in this work. “It certainly adds to what we know about the onset and diagnosis of cancer in different purebred dogs, which is certainly interesting and in the future will be important for people like me who are clinical veterinarians. “

Based on these results, along with evidence regarding tumor size and progression from previous studies in humans and dogs, the study authors recommend that all animals begin cancer screening at seven years of age and that breeds with a lower median age of diagnosis are screened earlier. . Being able to detect cancer earlier can allow veterinarians to offer families more treatment and care options, Flory says. PetDx offers a canine cancer blood test called OncoK9, which works by looking for cancer-associated mutations in DNA floating around outside cells. The test, which is available in North America, costs around $500. Liquid biopsy tests “are considered multi-cancer screening tests,” says Jill Rafalko, director of scientific communications at PetDx. “We are looking for any genomic alterations in the blood that could signal a variety of different cancer types that may be present in this dog.”

But experts not involved in this study are wary of cancer screening recommendations. A key problem, according to Cheryl London, a veterinary oncologist at Tufts University, is the lack of effective tools for early detection of canine cancer. “If we’re talking about real cancer screening, we don’t yet have the tools in veterinary medicine to actually do that,” London says. Tools commonly used in veterinary practices, such as ultrasounds and x-rays, aren’t sensitive enough to detect most early cancers — and based on data published by PetDx to date, liquid biopsies aren’t. not either, she adds. (London is a member of the Scientific Advisory Board of A healthcare companya California-based company specializing in personalized diagnostics and therapies for canine cancer.)

PetDx posted a OncoK9 validation study in PLOS ONE in 2022. It reported an overall sensitivity (the ability to identify true cases) of 54.7% and specificity (the ability to avoid detecting false positives) of 98.5%. In general, the detection rate of the test was much higher for larger and more advanced cancers: while the rate for large metastasized cancers was 87.5%, that for small localized cancers was only 19, 6%.

Another problem is that the team based its recommendation to screen two years before the median age of diagnosis solely on modeling the physical characteristics of the tumours, Moses says. As a veterinarian, “I’m much more concerned with issues like morbidity and quality of life,” she adds. What’s missing, according to Moses, are studies showing that early detection will lead to tangible benefits for the health and well-being of dogs. “As a clinician, I need a lot more information to know if knowing this information earlier is going to help me help dogs,” she says.

London notes that while the data from this study is helpful in confirming previously identified patterns in canine cancer diagnoses, the fact that a company selling a cancer screening test makes a recommendation as to when to start using the test is a “major conflict”. of interest.” Based on the information currently available, “we don’t have the ability to make a screening recommendation,” London says. “You’re asking people to spend a lot of money. The consumer needs to be aware of what the tests can and can’t do. And right now they can’t detect cancer at an early stage, period.”