Gut Microbiome Can Impact Immunotherapy Response

Gut microbiome may impact immunotherapy response in patients with cancer, according to Ryan Weight, DO, MD, assistant professor of medicine-medical oncology at the University of Colorado School of Medicine.

Weight, who presented research on the topic at the 2019 ASCO Annual Meeting, recently sat down with Oncology Nursing News to discuss the importance of a healthy microbiota, and what patients can do to improve it.

Oncology Nursing News: What do we know about the role of the microbiome in maintaining balance in the immune system?

Weight: We're learning more about the microbiome everyday through ongoing studies. We are starting to gain an understanding of its importance and its role within the response to immunotherapy and immune checkpoint blockade agents. From the data that is available, we understand that data suggests a diverse microbiome within the gut can improve response to immune checkpoint blockade across various tumor types.

What is some of the research that supports that?

There are a number of basic science studies and preclinical work that has been performed. Many of these studies that have been published to-date are on mouse models which have looked at the fecal microbiota of mice and their response to implanted tumors within the mice.

Some of the more interesting work that has been published is that if you perform a fecal microbiota transplant from a patient, say with melanoma, who had a response to their immune checkpoint blockade, if you take the feces from that patient and you transplant it, at least in a mouse model, also with melanoma, you can increase the response rate to immune checkpoint blockade in that mouse model through a fecal microbiota transplant.

Through some of that basic science and translational clinical work, we're beginning to understand the importance of both the diversity and the immune-specific role of the fecal microbiota in response to immune checkpoint blockade.

What is the role of diet in maintaining a diverse microbiome?

Even more recently, there has been a couple of studies that have come out that have found that agents that manipulate the gut microbiota can influence response to immune checkpoint blockades. Now these, keep in mind, are not large, randomized clinical trials, but they are some retrospective studies that have looked at response to immune checkpoint blockade based on the oral intake of the patients who have been receiving those agents. Some of the things that have been highlighted over the past couple of years have been things like probiotics, high-fiber diets, and antibiotics. All 3 of those have been shown to influence, at least retrospectively, the outcomes in patients receiving immune checkpoint blockade.

For example, there is a suggestion that antibiotics can reduce the diversity of the gut microbiome. Probiotics can also reduce the diversity of the gut microbiome, which may lead to a diminished response to immune checkpoint blockade. That's what these studies are suggesting. It needs to be bore out in large, randomized clinical trials, but it's an interesting thing to think about in our patients who are receiving these agents.

In addition to that, there is a suggestion that a high fiber diet can improve gut diversity, and therefore potentially improve the likelihood of response to immune checkpoint blockade. Again, more study is needed, but these are some interesting topics that are beginning to be looked at.