A trial to see if fibre can help to control side effects in people having radiotherapy that affects the bowel

Cancer type:

Anal cancer
Bladder cancer
Bowel (colorectal) cancer
Cervical cancer
Colon cancer
Ovarian cancer
Rectal cancer
Vaginal cancer
Vulval cancer
Womb (uterine or endometrial) cancer




Phase 1

This trial looked at if eating more or less fibre improved radiotherapy side effects to the bowel. It was for people having treatment to the area between their hip bones (pelvic radiotherapy).

More about this trial

Radiotherapy can be part of your treatment for cancer. It destroys cancer cells in the treated area. But it also affects healthy cells that are close by. New ways of giving treatment help to protect healthy tissue, but it can still be affected.
Radiotherapy to the organs in the area between your hip bones (your pelvis Open a glossary item), can cause inflammation Open a glossary item of your bowel. This causes loose poo, diarrhoea and difficulty controlling your bowels.
Researchers in this trial were interested in how diet could be used to protect the bowel  tissue. In this trial, they wanted to see if diets high or low in fibre Open a glossary item were better for people having radiotherapy. 
Asking people to reduce their fibre may help to stop the bowels opening too much. But increasing fibre may soak up more water from the bowel and give a better structure to the poo, making it pass through more slowly and steadily. Both approaches seemed to make sense. 
But more research was needed to find out which advice was best. The researchers believed that stopping these bowel symptoms happening could make treatment easier to give. And also reduce the risk of long term side effects
The main aims of this trial were to see if:
  • changing the amount of fibre eaten during a course of radiotherapy affected side effects
  • the amount of bowel that got a particular dose of radiotherapy affected the side effects 

Summary of results

The trial team found that eating a high fibre diet during a course of radiotherapy to the pelvis reduced the side effects.
This phase 1 trial was randomised. 166 people took part. Everyone who took part was put into 1of 3 treatment groups. Neither they or their doctor chose which group they were in. 
During their radiotherapy treatment:
  • 55 people had a low fibre diet 
  • 55 people had their usual diet 
  • 56 people had a high fibre diet 

Everyone kept a diary of:
  • what they ate
  • their bowel habits
  • the appearance of their poo
They also completed a questionnaire:
  • every week during their radiotherapy
  • at the end of treatment
  • 1 year after treatment 
The questions asked about side effects and how they were managing. 
The researchers compared the diaries and the questionnaires of each group. 
When the team looked at the diaries. They found that there was a significant difference Open a glossary item in the amount of fibre each group were eating. 
The researchers looked at what each group ate and if there was a difference in the amount of:
  • energy
  • protein 
  • fat
They found the amount of each was significantly lower in those who had the low fibre diet and their usual diet. 
Each answer in the questionnaire had a score. The team compared the total score of each person’s questionnaire to find out the results. 
The team looked at the scores from the start of treatment and the lowest score. Within each group there was no significant difference in these scores. 
They then compared the change in the scores from the start of radiotherapy to those at the end of radiotherapy. They found there was a smaller change in the high fibre group than those in the usual diet group. 
A year after radiotherapy people in the high fibre diet had a better score than those who had their usual diet. The team said this was a significant difference. 
People advised to have a high fibre diet during their pelvic radiotherapy had fewer immediate and long term side effects than those who had their usual diet. 
Advice to have a low fibre diet during pelvic radiotherapy has no evidence and should not be given to people in this situation. 
We have based this summary on information from the research team. The information they sent us has been reviewed by independent specialists (peer reviewed Open a glossary item) and published in a medical journal. The figures we quote above were provided by the trial team who did the research. We have not analysed the data ourselves.

Recruitment start:

Recruitment end:

How to join a clinical trial

Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Chief Investigator

Dr HJN Andreyev
Dr S Essapen

Supported by

The Royal Marsden NHS Foundation Trust

If you have questions about the trial please contact our cancer information nurses

Freephone 0808 800 4040

Last review date

CRUK internal database number:


Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Last reviewed:

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