A dog’s chances of surviving cancer treatment may depend on something invisible: the bacteria living in its gut.
An early clinical trial led by scientists at Oregon State University has found that canine cancer patients given a new form of immunotherapy lived longer or shorter depending on the make-up of their microbiome – the trillions of microorganisms that inhabit the digestive tract.
The findings, published in Veterinary Oncology, could signal a shift towards more personalised cancer care for dogs.
Cancer remains the leading cause of death in older dogs. Of the more than 87 million domesticated dogs in the United States, around one in four will develop cancer at some point. More than four million die from the disease each year, and roughly half of all dogs that reach the age of 10 will succumb to it.
The study was led by Natalia Shulzhenko, who studies host-microbiota interactions at Oregon State University’s Carlson College of Veterinary Medicine, and co-led by Andrey Morgun of the OSU College of Pharmacy.
“Our study is a first step toward using the gut microbiome as a tool to develop prognoses and to manipulate cancer, not just in dogs, but potentially as a model for human treatments as well,” Shulzhenko said.
The trial involved 51 dogs of different ages and breeds diagnosed with a range of cancers, including malignancies of the bone and blood vessels. Each was treated with an experimental cancer vaccine designed to stimulate the immune system to block two proteins that tell cancer cells to grow and divide.
Before treatment, researchers collected rectal swabs to analyse the dogs’ microbiomes. Although around 240 species account for more than 80 per cent of the canine microbial community, the overall ecosystem contains trillions of organisms.
Among them, the scientists identified 11 specific types of bacteria linked to survival outcomes. Some were associated with longer survival following treatment; others were linked to shorter life expectancy.
“In the future, an analysis of a microbiome swab could help predict how well a dog might respond to a cancer treatment,” Shulzhenko said. “This allows pet owners and vets to make more informed decisions about care. And now that we know certain bacteria are linked to survival, we can explore ways to ‘fix’ a dog’s gut microbiome to help the vaccine work better and help the dog live longer.”
The research was funded by the National Cancer Institute of the National Institutes of Health, the Canine Cancer Alliance and the Biomedical Sciences Department of the Carlson College of Veterinary Medicine. The collaboration included scientists from the National Cancer Institute, Yale University and the Bridge Animal Referral Center.
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