Low-Fiber Diet or High-Fiber Diet in Preventing Bowel Side Effects in Patients Undergoing Radiation Therapy for Gynecological Cancer, Bladder Cancer, Colorectal Cancer, or Anal Cancer


RATIONALE: Fiber may lessen bowel side effects caused by radiation therapy. It is not yet known whether a high-fiber diet is more effective than a low-fiber diet in preventing bowel side effects caused by radiation therapy.

PURPOSE: This randomized clinical trial is studying a high-fiber diet to see how well it works compared with a low-fiber diet in preventing bowel side effects in patients undergoing radiation therapy for gynecological cancer, bladder cancer, colorectal cancer, or anal cancer.

Full Title of Study: “A Randomized Controlled Trial to Investigate the Role of Low or High ‘Fibre’ Diets in Patients Undergoing Pelvic Radiotherapy – The Fibre Study”

Study Type

  • Study Type: Interventional
  • Study Design
    • Allocation: Randomized
    • Primary Purpose: Supportive Care
    • Masking: None (Open Label)
  • Study Primary Completion Date: December 2012

Detailed Description



- To compare the efficacy of a high- vs low-fiber intervention in preventing bowel toxicity in patients receiving radical pelvic radiotherapy treatment for gynecological, urological (bladder), colorectal, or anal malignancy.

- To compare whether a high- or low-fiber intervention has any beneficial effect over no intervention (i.e., ad-libitum fiber consumption).

- To examine the effect of a low- or high-fiber diet on gastrointestinal symptoms, measured using the IBDQ-B and Bristol Stool Chart, in patients receiving radical radiotherapy for pelvic malignancies.

- To minimize any potential risk associated with change in fiber intake by using a controlled and gradual dietary-based intervention combined with dietetic advice.


- To examine the relationship between volume of irradiated bowel and onset of gastrointestinal symptoms as measured by the Bristol Stool Chart.

- To measure percentage compliance with fiber prescription through validated dietetic techniques including the 7-day Food Diary using household measures and the 24-hour recall.

OUTLINE: Patients are stratified according to disease (gynecological vs gastrointestinal) and concomitant therapy (received vs not received). Patients are randomized to 1 of 3 treatment arms.

- Arm I (low-fiber diet): Patients are assessed by a qualified dietitian, receive written guidance, and are counseled as to how best to meet their study fiber prescription of a low-fiber diet, comprising 'not more than' 10 g of fiber per day for up to 7 weeks.

- Arm II (high-fiber diet): Patients are assessed by a qualified dietitian, receive written guidance, and are counseled as to how best to meet their study fiber prescription of a high-fiber diet, comprising a target of between 18 and 22 g of fiber per day for up to 7 weeks.

- Arm III (no intervention): Patients receive advice designed to ensure they maintain their normal habitual diet for up to 7 weeks.

All patients undergo radiotherapy once daily comprising approximately 25 (or more) fractions in total to be delivered for 5-7 weeks in the absence of unacceptable toxicity.

All patients are asked to complete two 7-day Food Diaries at baseline and end of radiotherapy treatment. All patients keep a daily record of stool characteristics and frequency using the Bristol Stool Chart. Patients also complete a short 1-page weekly-cost questionnaire to assess the economic impact of symptom management. Patients in arms I and II complete several additional questions regarding the costs (if any) of adhering to their fiber prescription and the palatability of the diet.

Blood and stool samples may be collected at baseline and during study therapy for biomarker analysis.

After completion of study treatment, patients are followed up for up to 1 year.


  • Dietary Supplement: dietary intervention
  • Other: laboratory biomarker analysis
  • Procedure: gastrointestinal complications management/prevention
  • Procedure: management of therapy complications
  • Radiation: selective external radiation therapy

Clinical Trial Outcome Measures

Primary Measures

  • Change in IBDQ-B (Inflammatory Bowel Disease Questionnaire – Bowel Subset) score between baseline (i.e., Day 1 of radiotherapy treatment) and the nadir score during treatment

Secondary Measures

  • Incidence of toxicity, defined using the Bristol Stool Chart
  • Costs for symptom management

Participating in This Clinical Trial


  • Diagnosis of gynecological, urological (bladder), colorectal, or anal malignant cancer
  • Scheduled to undergo a course of radical or adjuvant pelvic radiotherapy (≥ 45 Gy)
  • Radiotherapy regimen will be delivered in daily fractions comprising approximately ≥ 25 fractions over 5-7 weeks


  • No prior prescribed low-residue diet for a clear medical reason
  • No established wheat intolerance or celiac disease
  • No concurrent condition precluding oral nutritional intake


  • No gastrointestinal stent
  • No jejunostomy, ileostomy, or colostomy
  • No concurrent participation in a study with toxicity as an endpoint

Gender Eligibility: All

Minimum Age: N/A

Maximum Age: 120 Years

Are Healthy Volunteers Accepted: No

Investigator Details

  • Lead Sponsor
    • Royal Marsden NHS Foundation Trust
  • Overall Official(s)
    • Peter R. Blake, MD, Study Chair, Royal Marsden NHS Foundation Trust
    • Jervoise Andreyev, MD, , Royal Marsden NHS Foundation Trust

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