A dog’s chances of surviving cancer may depend partly on the tiny organisms living inside its digestive system, according to a new study from Oregon State University.
Researchers found that dogs receiving an experimental cancer immunotherapy lived longer or shorter lives depending on the makeup of their gut microbiome — the vast community of bacteria and other microbes in the intestines.
Cancer is tragically common in dogs. In the United States, about one in four dogs will develop cancer during their lifetime, and it is the leading cause of death in older dogs.
With millions of pets affected each year, scientists are searching for better treatments and ways to predict which therapies will work best.
The study followed 51 dogs of different breeds and ages that had been diagnosed with various cancers, including bone cancer and cancers affecting blood vessels.
Each dog received a new type of cancer vaccine designed to stimulate the immune system. The vaccine works by blocking proteins that cancer cells use to grow and spread.
Before treatment began, researchers collected samples from the dogs’ digestive systems to analyze their microbiomes.
The gut contains trillions of microbes, and about 240 species make up most of this internal ecosystem. Scientists compared these microbial communities with how long the dogs survived after treatment.
They discovered that certain bacteria were strongly linked to outcomes. Eleven specific types of microbes stood out.
Some were associated with longer survival times, suggesting they may help the immune system fight cancer more effectively. Others were linked to shorter survival, hinting that they could interfere with treatment or weaken the body’s response.
The findings suggest that a simple microbiome test could one day help veterinarians predict how well a dog will respond to cancer therapy. This could allow pet owners and doctors to choose treatments more wisely and tailor care to each animal’s unique biology.
Researchers also believe it may be possible to improve outcomes by changing the gut microbiome itself. Future treatments could include special diets, probiotics, or other methods designed to encourage beneficial bacteria and reduce harmful ones. By adjusting the microbial balance, scientists hope to make immunotherapy more effective and help dogs live longer.
Beyond helping pets, the research may also have implications for human medicine. Dogs share many similarities with humans in how cancers develop and respond to treatment, making them valuable models for studying disease.
Insights gained from canine patients could eventually guide new approaches to cancer therapy for people as well.
While the study is still an early step, it highlights the growing recognition that the gut microbiome plays a powerful role in health and disease.
For millions of families who consider their dogs part of the family, this research offers hope that personalized treatments based on gut bacteria could someday improve survival and quality of life for beloved pets facing cancer.
