Introduction The anti-inflammatory role of dietary fibre, its impact on bowel frequency and stool consistency is inadequately studied. Therapeutic radiotherapy for prostate cancer provides a unique opportunity to assess the potential efficacy of fibre in protecting the rectum from cumulative, radiation-therapy induced, inflammatory insults. The rectum inevitably receives some radiation dose during prostate irradiation. Rectal function in most men, will be normal before the radiotherapy starts and a predictable inflammatory response occurs during radiotherapy which peaks during the second week of treatment, causing the worst symptoms by the fourth to fifth weeks.
We investigated whether patients could follow a fluid and fibre prescription designed to regularise bowel habit commencing before and continuing for the 6–9 weeks of radiotherapy. Additionally, the effect of the diet on gastrointestinal symptoms, rectal distension and stool consistency was examined.
Methods Fibre and fluid intake was assessed at baseline and individualised prescriptions given to regularise frequency of bowel motion to at least 1 motion/day and ensure adequate fluid intake. Compliance was measured daily as was stool frequency and type (consistency) using the Bristol Stool Form 7-point scale. Symptoms were assessed at baseline and at end-RT (end of radiotherapy) using a modified IBDQ (Inflammatory Bowel Disease Questionnaire) and IBDQ-B, bowel subset. Rectal gas (5-point scale) and distension (rectal Cross Sectional Area in cm2) defined as rectal volume/length were measured throughout treatment from serial CT scans.
Result 22 patients were invited to participate. 21 (median: 71 years; range: 59–82 years) provided evaluable data. Between baseline and end-RT, 14 patients increased fibre intake (NSP: Englyst) and seven decreased intake (5 g/day and -2 g/day, respectively). 13 patients exceeded and eight patients did not meet their prescribed fibre intake. Stool frequency increased from mean 1.9 to 2.4 motions/day at end-RT. The mean fall in IBDQ-B scores (n=21) was 10.8 points which was similar in both the increasing and decreasing fibre groups (10.3 vs 11.6 points, respectively). The mean fall in IBDQ scores was twofold greater in the decreasing fibre group compared to increasing (34.6 vs 17.6, respectively). Rectal distension was significantly correlated with rectal gas (p=0.04) but was not associated with change in fibre intake. Mean rectal CSAcm2 decreased from 7.5 cm2 at baseline to 6.8 cm2 at end-RT.
Conclusion Patients are able to follow fibre prescriptions based on normally-consumed foods for prolonged periods but there is a tendency to exceed dose and therefore it is important to set upper limits. Increased fibre intake (25% more than habitually consumed) appeared to offer protection from symptoms and did not have an adverse effect on rectal gas, distension, stool frequency or consistency.
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