Effect of Pelvic Radiotherapy on the Intestinal Microbiome and Metabolome

Plain-language summary

Eight in ten patients will develop bowel problems during radiotherapy, eg diarrhoea, pain and incontinence, half will develop difficult long-term bowel problems. It is not known why some people get bowel problems and others do not and there is no test to predict who will develop bowel problems following their treatment. There is a link between the changes in the number and type of gut bacteria (the microbiome) in some bowel conditions and it is possible to test for these different bacteria in a simple stool sample using genetic testing. Also gut bacteria produce different gases in the stool called "volatile organic compounds" (VOCs), which can be measured in stool samples. Specific VOC patterns have been seen in other bowel conditions and small studies suggesting that there are specific VOC and gut bacteria patterns in the stool of those undergoing pelvic radiotherapy which may help to identify people who will get difficult bowel problems. Diet can change the microbiome/VOCs so diet change could improve bowel symptoms after radiotherapy. The investigators 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/type of gut bacteria and VOCs between those who get severe bowel symptoms compared to those with mild bowel symptoms. They also want to see whether these differences in VOCs or gut bacteria can tell who will develop severe bowel symptoms 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 study would work. This will make sure the investigators can recruit and consent people safely and will test the best ways of measuring bowels symptoms using several questionnaire options. They will collect the information needed to work out how many people would be needed in a large trial to fully test the theory. Ultimately, the investigators would like to use differences in the number/type of gut bacteria and VOCs to find ways to better prevent and treat bowel problems after pelvic radiotherapy.

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