Investigating the effect of pelvic radiotherapy on the intestinal microbiome and metabolome to improve the detection and management of gastrointestinal (GI) toxicity
Radiotherapy has many side-effects that lower a patient’s physical and mental wellbeing, this includes bowel problems such as diarrhoea and incontinence. This research will potentially lead to a simple test that will predict who will have more severe bowel problems before radiotherapy, and provide information on how diet can manage those side-effects.
8 in 10 patients will develop bowel problems during radiotherapy – these include diarrhoea, pain and incontinence – and half will develop difficult long-term bowel problems. We do not know why some people get bowel problems and others do not, and we do not have a test to predict who will develop bowel problems following their treatment.
There is a link between the changes in the number and type of bacteria in the gut (the gut microbiome) in some bowel conditions and we can test for these different bacteria in a simple stool sample using genetic testing. Furthermore, gut bacteria produce different gases in the stool called “volatile organic compounds” (VOCs), these can be measured in stool samples.
Specific VOC patterns have been seen in other bowel conditions and previous small studies suggest that there are specific VOC and gut bacteria patterns in the stool of those undergoing pelvic radiotherapy, and these can be used to identify people who will get bowel problems. Diet can change the microbiome and VOCs, so changing your diet could improve bowel symptoms after radiotherapy.
We would like to test stool samples of patients with womb, cervix, or bladder cancer having pelvic radiotherapy to see if there are differences in the number and type of gut bacteria and VOCs between those who get severe bowel problems compared to those with mild bowel problems. We also want to see whether differences in VOCs or gut bacteria can tell who will develop severe bowel problems during or after radiotherapy and determine the effect of diet.
The first step is to run the study on a small scale to confirm that a larger, more in-depth study would work. This will make sure we can recruit and consent people safely and will test the best ways of measuring bowels problems using several questionnaire options. We will collect the data needed for us to work out how many people we would need in a large trial to fully test our theory. Ultimately, we would like to use differences in the number and type of gut bacteria and VOCs to find ways to better prevent and treat bowel problems after pelvic radiotherapy.
People referred to The Christie Hospital for pelvic radiotherapy will be invited to be in the study, given information, and a chance to talk to researchers. Those who agree to be involved will bring stool samples on the first day of their radiotherapy, their 20th radiotherapy treatment and to their clinic appointment six months after radiotherapy. They will also fill in three short questionnaires about their bowels and quality-of-life, and complete food diaries for three days before each appointment. Stool samples will be tested for VOCs and bacteria to look for differences in people who have the worst bowel problems and those who have the least bowel problems according to the questionnaires.
This simple stool test will allow doctors to predict who will get radiotherapy-related bowel problems and then tailor their treatment accordingly. It will help us understand what changes in the gut cause the symptoms and what treatments may help.
