top of page

Gut Microbiome and Dog Cancer

Updated: Apr 19, 2023

Cancer risks and treatment response are influenced by gut microbiome.

The gut microbiome, a term used to describe the trillions of microbes living in an organism’s digestive tract, has recently gained lots of attention in the scientific community.

What makes the gut microbiome so special?

Think of the gut microbiome as a fingerprint - each person has a completely unique and original gut microbiome shaped by their environment and lifestyle.

Diet, exercise, stress, genetics, and medications (such as antibiotics) are all factors that affect the composition of one’s gut microbiome.

Through recent studies, the gut microbiome has been linked to multiple diseases including diabetes, arthritis, and cancer. The interactions between gut bacteria and their metabolites and the rest of the body can also impede or enhance the effects of treatments.

All of this applies to dogs too!

Gut Microbiome can raise (or reduce ) cancer risks

Several studies have linked imbalances in the gut microbiome to an increased risk of various types of cancer.

One way in which the gut microbiome influences cancer risk is by modulating the immune system, which can either promote or suppress the growth of cancer cells.

For example, canines with dysbiosis, an imbalance of their gut microbiome, display increased inflammation associated with several forms of cancer.

Additionally, some strains of bacteria in the gut have been shown to produce carcinogenic compounds or metabolize nutrients in a way that increases the risk of cancer.

Conversely, some bacteria may have protective effects against cancer.

For example, several studies have suggested that consuming prebiotics (e.g. fiber) and probiotics, which are live microorganisms that can confer health benefits when consumed in adequate amounts, may reduce the risk of developing certain types of cancer.

Gut Microbiome can reduce the cancer treatment side effects

Cancer patients receiving chemotherapy treatment often experience nausea and diarrhea, displaying symptoms of Chemotherapy-induced Gastrointestinal Toxicity, a condition that can develop through changes in the gut microbiome.

Probiotic supplements have been found to be beneficial and well-tolerated to help reduce such symptoms in dog patients.

Fasting (for 24-48 hrs prior to chemotherapy) is another way to help reduce the undesirable side-effect during chemotherapy treatment too.

Gut Microbiome can change the efficacy of cancer treatment

A growing number of studies in the laboratory and in human clinical studies support the importance of the role that the gut microbiome plays in determining the efficacy of cancer treatments.

Numerous studies have found a strong association between the gut microbiome and how the immune system responds to ICI (immune checkpoint inhibitor) immunotherapy.

Those patients with certain gut microbiome composition and diversity respond better to ICI therapy and become long-term survivors, many becoming cancer-free. In contrast, patients with undesired gut microbiome composition didn’t respond to the therapy.

Helping more patients respond to cancer immunotherapy

Today there are several immunotherapy treatments available for dogs.

But clinical benefits are only observed in a subset of patients. Some dogs respond strongly and experience durable remission. But other dogs show little response.

Modifying the gut microbiome may be one strategy to help more dogs become responders and become long-term survivors.

What is a form of treatment related to the gut microbiome?

A treatment known as Fecal Microbiota Transplant (FMT) is starting to help human cancer patients.

With this therapy, a fecal sample is transferred from a patient who benefited from immunotherapy to patients who did not respond to immunotherapy.

In a recent study with human patients with melanoma, fecal samples were obtained from 2 melanoma patients that had previously received immunotherapy and had achieved a complete remission. The samples were then administered to 10 melanoma patients who had not responded to immunotherapy.

"By modifying the gut microbiome, you can turn some non-responders into responders for certain immunotherapy treatments."

Out of the 10 patients who received an FMT, 3 were observed to respond positively, either achieving partial or full remission when the same immunotherapy treatment was again administered alongside FMT. Additionally, no major adverse responses to the FMT were observed.

So by modifying the gut microbiome, you can turn some non-responders into responders for immunotherapy treatment.

Can fecal microbiota transplants be used to treat canine patients?

So far, FMT for canines has primarily been used for treating diarrhea and inflammatory bowel diseases, and multiple studies have shown FMT treatment to be beneficial in treating these conditions.

A new study at Oregon State University supported by Canine Cancer Alliance is investigating the relationship between dog's gut microbiome and immunotherapy response. Fecal samples are collected from dogs receiving cancer vaccine treatment and are being analyzed.

Such a study may lead to FMT being offered as part of a cancer therapeutic option for your canine companion in the future!


The gut microbiome has a significant influence on your dog’s health.

A healthy gut microbiome may reduce the risk of tumor growth, and may even increase the efficacy and reduce the side effects of cancer treatments.

Researchers are seeking a better understanding of the link between the gut microbiome and cancer, to help dogs avoid cancer or to help dogs be treated more safely and effectively.

Life-saving studies supported by Canine Cancer Alliance are made possible by donations from loving pet parents.


  1. Bull, Matthew J, and Nigel T Plummer. “Part 1: The Human Gut Microbiome in Health and Disease.” Integrative medicine (Encinitas, Calif.) vol. 13,6 (2014): 17-22.

  2. Gilbert, Jack A et al. “Current understanding of the human microbiome.” Nature Medicine vol. 24,4 (2018): 392-400. doi:10.1038/nm.4517

  3. Middelbos IS, Vester Boler BM, Qu A, White BA, Swanson KS, et al. “Phylogenetic Characterization of Fecal Microbial Communities of Dogs Fed Diets with or without Supplemental Dietary Fiber Using 454 Pyrosequencing.” (2010) PLOS ONE 5(3): e9768.

  4. Hand D, Wallis C, Colyer A, Penn CW “Pyrosequencing the Canine Faecal Microbiota: Breadth and Depth of Biodiversity.” (2013) PLOS ONE 8(1): e53115.

  5. Rachel, Pilla, and Jan S. Suchodolski. “The Role of the Canine Gut Microbiome and Metabolome in Health and Gastrointestinal Disease.” Frontiers in Veterinary Science vol. 6 (2019): 2297-1769 10.3389/fvets.2019.00498

  6. Beynen, Anton. (2020). Beynen AC, 2020. Diet and canine cancer. 137-148.

  7. Niina, Ayaka et al. “Fecal microbiota transplantation as a new treatment for canine inflammatory bowel disease.” Bioscience of microbiota, food and health vol. 40,2 (2021): 98-104. doi:10.12938/bmfh.2020-049

  8. Zheng, Hui-Hua et al. “The Relationship of Tumor Microbiome and Oral Bacteria and Intestinal Dysbiosis in Canine Mammary Tumor.” International journal of molecular sciences vol. 23,18 10928. 18 Sep. 2022, doi:10.3390/ijms231810928

  9. Araji, Ghada et al. “The Emerging Role of the Gut Microbiome in the Cancer Response to Immune Checkpoint Inhibitors: A Narrative Review.” Journal of Immunotherapy and precision oncology vol. 5,1 13-25. 16 Nov. 2021, doi:10.36401/JIPO-21-10

  10. Jugan, Maria C et al. “Preliminary evaluation of probiotic effects on gastrointestinal signs in dogs with multicentric lymphoma undergoing multi-agent chemotherapy: A randomized, placebo-controlled study.” Veterinary record open vol. 8,1 e2. 29 Mar. 2021, doi:10.1002/vro2.2

  11. Baruch, Erez N., et al. "Fecal microbiota transplant promotes response in immunotherapy-refractory melanoma patients." Science 371.6529 (2021): 602-609.


bottom of page