The Role of Gut Microbiota in Cancer Immunotherapy Responses

Cancer immunotherapy, or leveraging the immune system to treat cancer, is a powerful approach to fighting a diverse disease. While only six active immunotherapies have been approved for cancer treatments, hundreds of others are being tested in clinical trials, and for good reason – in some instances, immunotherapy drugs have bolstered patients’ immune systems well enough to drive cancer into remission, with only a few side effects. Unfortunately, one of the limitations of these drugs is the variability of their effectiveness. Despite some remarkable successes, there are just as many patient stories of immunotherapy drugs failing to deliver any therapeutic benefits. Naturally, researchers have been probing both patient populations to understand what factors might be influencing immunotherapy efficacy. Surprisingly, a team of researchers has discovered recently that gut microbiota may be playing a meaningful role in determining patients’ responses to immunotherapy treatments.


Following a study of oral and fecal samples taken from more than 200 immunotherapy patients with an advanced type of skin cancer, researchers from the University of Texas MD Anderson Cancer Center found that having a more diverse gut microbiome was linked to a better response to immunotherapy treatment. Specifically, the research showed that the patients who had responded positively to a certain immunotherapy drug had more members from the Ruminococcaceae family of Clostridium bacteria than did the patients who did not respond to the same immunotherapy treatment. What’s more, the researchers found that those patients who did not respond to the treatment had more bacteria from the order Bacteroidales.


Given that the gut microbiome has already been shown to play a critical role in immune system function, there’s good reason to believe bacteria can impact immunotherapies. However, it will take further research and quality clinical trials to determine if these bacteria are causing the patients to have different responses to immunotherapies or if they are simply correlated with the patients’ responses.


To learn more about the MD Anderson Cancer Center study results, check out the researchers findings, which were presented recently at the ASCO-SITC Clinical Immuno-Oncology Symposium.