Dietary fibre supplementation to reduce side effects of prostate radiotherapy (DIETRICH study)
| ISRCTN | ISRCTN87108662 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN87108662 |
| Integrated Research Application System (IRAS) | 355096 |
| Central Portfolio Management System (CPMS) | 72064 |
| Sponsors | University of Aberdeen, NHS Grampian |
| Funder | Prostate Cancer UK |
- Submission date
- 01/12/2025
- Registration date
- 06/01/2026
- Last edited
- 23/01/2026
- Recruitment status
- Not yet recruiting
- Overall study status
- Ongoing
- Condition category
- Cancer
Plain English summary of protocol
Background and study aims
One of the treatments for prostate cancer is radiotherapy. Whilst this can help to treat the cancer, it
can lead to bowel and bladder complications such as diarrhoea, discomfort, more frequent urination
and bleeding. Approximately 1 in 2 men can suffer from these side effects. Side-effects can remain
for some time once treatment is completed which leads to further complications and can affect
quality of life.
There is evidence that a dietary fibre supplement may help with some radiotherapy side effects. In
the DIETRICH study, we want to investigate if men who have their diet supplemented with a dietary
fibre source called inulin before radiotherapy starts, during treatment and for a short time after, have
fewer gut-associated side effects than those who do not take extra fibre. Inulin is a natural
substance from plants such as chicory root. It works by boosting the good bacteria in the gut which
helps to reduce inflammation in the lower gut and might lead to fewer side-effects.
Who can participate?
We aim to recruit 220 men who have opted for radiotherapy treatment for their prostate cancer.
What does the study involve?
Half the men who take part in DIETRICH will be given a supply of inulin to take for 2 weeks before
radiotherapy, 4 weeks during radiotherapy and for 3 weeks after. The other half will receive a
treatment which will look and taste similar to inulin but will not include any fibre (placebo treatment).
Participants will not know what treatment they are given. Participation in the DIETRICH study will be
for a total of 18 weeks. During this time participants will answer some questions on symptoms and
diet. Faecal (poo) samples will be collected before and after radiotherapy to study the bacteria and
substances in them. This will help us understand how inulin may reduce side-effects and improve
gut health.
What are the possible benefits and risks of participating?
You may experience fewer gut-related side effects from radiotherapy, but this cannot be guaranteed. Taking part will help researchers learn more about how diet can improve gut health during cancer treatment. Risks are minimal, but some people may experience mild digestive changes from the fibre supplement.
Where is the study run from?
University of Aberdeen (UK)
NHS Grampian (UK)
When is the study starting and how long is it expected to run for?
January 2026 to February 2028
Who is funding the study?
Prostate Cancer UK
Who is the main contact?
dietrich@abdn.ac.uk
Contact information
Public
DIETRICH Trial Office, CHaRT, University of Aberdeen, Health Sciences Building, Foresterhill
Aberdeen
AB25 2ZD
United Kingdom
| Phone | +44 1224 438103 |
|---|---|
| dietrich@abdn.ac.uk |
Principal investigator, Scientific
Rowett Institute, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill
Aberdeen
AB25 2ZD
United Kingdom
 ORCID ID |
0000-0001-7208-2912 |
|---|---|
| Phone | +44 1224 438651 |
| anne.kiltie@abdn.ac.uk |
Study information
| Primary study design | Interventional | |
|---|---|---|
| Allocation | Randomized controlled trial | |
| Masking | Blinded (masking used) | |
| Control | Placebo | |
| Assignment | Parallel | |
| Purpose | Health services research, Prevention, Treatment | |
| Scientific title | Phase 2 randomised controlled trial of effects of the dietary fibre supplement inulin versus placebo on intestinal and urinary side effects in men receiving standard of care radiotherapy for intermediate/high risk localised or locally advanced prostate cancer | |
| Study acronym | DIETRICH | |
| Study objectives | Primary Objective The primary objective is to evaluate if supplemental inulin starting two weeks prior to and during radiotherapy is advantageous over treatment as usual (which may include rescue psyllium husk or other medication as part of standard of care when bowel symptoms develop during treatment). The primary outcome will be measured by the bowel domain of EPIC-26 at 4-weeks after starting radiotherapy. Secondary Objectives (a) Does inulin supplementation: 1. Reduce acute urinary toxicity, as assessed by both EPIC-26 urinary domains? 2. Reduce bowel and bladder toxicity in clinician-reported assessments, measured using the Common Terminology Criteria for Adverse Events (CTCAE)? 3. Improve overall quality of life and reduce treatment related symptoms (measured by EORTC QLQ-C30) b) To evaluate changes in the bacterial composition and resulting metabolites, including short-chain fatty acids (SCFAs), in faecal samples of men before and after inulin/placebo supplementation and radiotherapy, using 16S rRNA gene sequencing and gas chromatography, respectively. This data will be compared with intestinal and urinary toxicity, as well as food and nutrient intake. c) To assess the effect of inulin/placebo supplementation on intestinal inflammatory responses (via calprotectin levels in faeces) to radiotherapy. d) To assess the feasibility of identifying surrogate biomarkers that distinguish responders from non-responders to inulin in terms of reduction in acute radiotherapy toxicity. This will involve 16S sequencing and other translational biomarkers (e.g., calprotectin, SCFAs) and will contribute to the development of biomarkers for a future Phase 3 clinical trial. e) To determine participants' habitual diet at baseline and Week 16. This will include the assessment of baseline fibre intake and diet quality, as well as the pro- or anti-inflammatory nature of the habitual diet. Additionally, the study will explore any dietary changes or improvements resulting from participants' involvement in the study. Tertiary Objectives To assess hormonal and sexual function in response to inulin/placebo supplementation (measured by the hormonal and sexual domains of the EPIC-26). | |
| Ethics approval(s) |
Approved 12/12/2025, London - Central Research Ethics Committee (3rd Floor, 3 Piccadilly Place, London Road, HRA Manchester Centre, Manchester, M1 3BN, United Kingdom; +44 207 1048285; londoncentral.rec@hra.nhs.uk), ref: 25/LO/0887 | |
| Health condition(s) or problem(s) studied | Prevention of acute bowel toxicity and urinary side effects in men undergoing radiotherapy for prostate cancer. | |
| Intervention | We will aim to recruit 220 men who have opted for radiotherapy treatment for their prostate cancer. Half the men who take part in DIETRICH will be given a supply of inulin to take for 2 weeks before radiotherapy, 4 weeks during radiotherapy and for 3 weeks after. The other half will receive a treatment (maltodextrin) which will look and taste similar to inulin but will not include any fibre (placebo treatment). Participants will be asked to take 16g daily of the inulin/maltodextrin (placebo); 8g in the morning and 8g in the evening. The inulin/maltodextrin (placebo) which will be in powdered form and can be added to cold drinks and taken orally. Participants will not know what treatment they are given. Participation in the DIETRICH study will be for a total of 18 weeks. During this time participants will answer some questions on symptoms and diet. Faecal samples will be collected before and after radiotherapy to study the bacteria and substances in them. This will help us understand how inulin may reduce side-effects and improve gut health. Randomisation will occur once all eligibility criteria are confirmed and informed consent obtained. A computerised randomisation system created by CHaRT will be used to randomise participants in a 1:1 ratio to inulin or maltodextrin (placebo), stratified by centre and nodal treatment (yes/no). | |
| Intervention type | Supplement | |
| Primary outcome measure(s) |
| |
| Key secondary outcome measure(s) |
Tertiary outcome measures | |
| Completion date | 29/02/2028 |
Eligibility
| Participant type(s) | |
|---|---|
| Age group | Mixed |
| Lower age limit | 18 Years |
| Upper age limit | 100 Years |
| Sex | Male |
| Target sample size at registration | 220 |
| Key inclusion criteria | 1. Men with intermediate/high risk localised or locally advanced prostate cancer planned to receive radical radiotherapy to the prostate with or without pelvic nodes. 2. Have Cambridge Prognostic Group (CPG) 3, 4 or 5 prostate cancer 3. T1-3 N0 M0 4. Receiving radical radiotherapy to the prostate with or without pelvic nodes (60 Gy in 20 fractions over 4 weeks) 5. Age ≥18 years 6. Are able and willing to give informed consent to participate and to participate in study procedures 7. Have a WHO performance status 0-2 (well enough to perform daily activities with only mild restrictions identified at screening/first visit). |
| Key exclusion criteria | 1. T4 disease 2. History of colectomy, stoma (ileostomy or colostomy), or other major gastrointestinal surgeries altering bowel anatomy 3. Prior radiotherapy to the prostate or pelvis 4. Prior radical prostatectomy 5. Prior androgen deprivation therapy (ADT) for >12 months at randomisation 6. Patient to have rectal spacer inserted for radiotherapy 7. Poorly controlled diabetes mellitus (Patient reported) 8. Coeliac disease 9. Known allergy to maltodextrin (placebo) 10. Known allergy to inulin 11. Life expectancy <5 years 12. Men without capacity |
| Date of first enrolment | 01/04/2026 |
| Date of final enrolment | 30/06/2027 |
Locations
Countries of recruitment
- United Kingdom
- England
- Scotland
Study participating centres
Aberdeen
AB25 2ZN
Scotland
Edinburgh
EH4 2XU
Scotland
Glasgow
G12 0YN
Scotland
Leeds
LS9 7TF
England
Clatterbridge Road
Bebington
Wirral
CH63 4JY
England
Withington
Manchester
M20 4BX
England
Northwood
HA6 2RN
England
Preston
PR2 9HT
England
Results and Publications
| Individual participant data (IPD) Intention to share | No |
|---|---|
| IPD sharing plan summary | Not expected to be made available |
| IPD sharing plan |
Editorial Notes
23/01/2026: The following changes were made to the study record:
1. The date of first enrolment was changed from 01/01/2026 to 01/04/2026.
2. The ethics approval was added.
17/12/2025: Trial's existence confirmed by London - Central Research Ethics Committee.
