The gut microbiome is one of the most talked about topics in medical research. In the last two years, I've written articles about how its composition and health may be related to depression, multiple sclerosis and even response to cancer immunotherapy drugs. Recently, one of the world's biggest cancer charities, Cancer Research UK has dedicated $25 million to several international teams of researchers, who aim to explore new links between the microbiome and colorectal cancer.
Now, researchers in the U.K. have shown that the likelihood of developing damage to the gut after radiotherapy treatment for prostate or gynecological cancers is also linked to the gut microbiome. Radiotherapy is an important part of treatment for many patients with these cancers, but 10-25% of people treated this way have significant long-term damage to their gut, which impairs their quality of life.
"Radiotherapy to the prostate and pelvic lymph nodes is an important way to manage cancer but it can result in damage to the gut and unpleasant side effects for the patient, which can often be long-lasting and quite severe," said David Dearnaley, senior author of the study, Professor of Uro-Oncology at The Institute of Cancer Research, London and Consultant Clinical Oncologist at The Royal Marsden NHS Foundation Trust.
The study published today in Clinical Cancer Research, looked at the bacterial fingerprint in fecal samples of 134 cancer patients at different stages of their treatment, including both before and after radiotherapy aimed at the prostate or lymph nodes near the gut. Their work showed that having a reduced diversity of gut bacteria was associated with both acute and long-term damage to the gut. Patients who had a high risk of gut damage from the treatment also had 30-50% higher levels of three specific types of bacteria; Clostridium IV, Roseburia and Phascolarctobacterium.
“Our study is the first to show that gut bacteria have an important influence on how susceptible patients are to gastrointestinal side effects from radiotherapy. We still need to do further studies to confirm the role of good bacteria, but if we can identify patients at the highest risk of gut damage we could intervene to control, treat or even prevent the side effects of radiation. If microbial treatments such as fecal transplants are found to reduce damage, for example, it could substantially improve patients’ quality of life,” said Dearnaley.
Fecal transplants are exactly what they sound like. Transplanting the feces of one person into another with the hope of improving their microbiome. However disgusting this may seem to some, the procedure has had a lot of success in treating antibiotic-resistant infections with "hospital superbug" Clostridium difficile. However, after many positive results, the procedure recently resulted in an FDA warning after a person died from E.coli after receiving a fecal transplant from someone infected with the bacteria.
The new research is the first to look at the possible protective effects of the gut microbiome in preventing the long-term side effects of radiotherapy although exactly why a particular microbiome composition is better for avoiding these side-effects is currently unclear. The next step is to look at whether the researchers can use this bacterial fingerprint information to identify people at high risk of developing debilitating gut side effects from radiotherapy and intervene safely, whether by fecal transplants or another means.