Which bowel preparation is best?

Comparison of bowel preparation (high fibre diet, daily micro-enema) and no bowel preparation in prostate cancer patients treated with radical radiotherapy to assess the effect of bowel preparation on prostate shifts.

There is strong evidence that, in patients treated without IGRT, rectal distension at a patient’s treatment planning scan can lead to geographical miss, which in turn reduces biochemical control and local control [1]. Although there are other possible variables in prostate radiotherapy e.g. bladder filling, rectal distension is the single most important variable in causing prostate motion in the antero-posterior direction [2-4]. There are several techniques to reduce rectal distention and consequent prostate shifts are in common use in the UK including a high fibre diet, laxatives and micro-enemas however there is paucity of randomized data confirming the best bowel preparation. Hence, this audit was performed to assess our current practice and to have standard departmental guidelines on best bowel preparation to minimize rectal distension.

The standard: 

De Crevoisier et al. showed rectal cross sectional area (CSA)>11.2cm2 as an independent predictor of increased risk of biochemical failure [1]. Fiorino et al assessed setup and organ motion by analysing daily MVCT of patients [5]. In cases of a distended rectum as evident by the MVCT, rectum emptying procedures were carried out. This lead to reduction in fraction of 5mm or greater PA shift of prostate relative to bony anatomy from 2.2% to 0.7%, with no shifts greater than 6mm after bowel emptying procedures. The study reported daily self-application of enemas to be highly effective in reducing prostate motion because of rectal emptying. Application of enema may lead to a reduction in the geographical miss, even in the absence of the Image Guided Radiotherapy (IGRT) technology use.

Target: 

To achieve reduction in prostate shift of <5mm and CSA (rectal cross sectional area) <11.2cm2.

Indicators: 

• Reduction in rectal CSA <11.2cm2

• Reduction in prostate shift to <5mm

Data items to be collected: 

Excel spreadsheet used to collect and analyse data includes the following information:

1. Rectal CSA to be calculated by dividing total rectal volume (including organ contents such as faeces and gas)by its length

2. Relative CSA is calculated by dividing the verification scan CSA by planning scan CSA. This gives variability of bowel volume on repeated verification scans as compared to the planning scan

3. Excel sheet to be used to collate the data for each of the three sample

4. Record left to right shift as x (x +ve = left, x-ve = right), the anteroposterior shift as y (y+ve = anterior, y-ve = posterior) and superioinferior shift as z (z+ve = superior, z-ve=inferior)

Suggested number: 

• 10 patients per sample cohort (30 patients in total)

• Comparison of the planning CT scan and weekly verification CBCT scans (85 pre leaflet, 89 post leaflet and 89 post enema)

1. Explore other methods to achieve prostate shift of <5mm e.g use of different bowel preparation procedures including laxatives and / or use of IGRT for all patients treated with radical intent

2. Re-audit in 12 months to assess adherence to the use of bowel preparation

• Personnel : Audit lead , research radiographer and physicist to retrieve archived images, audit contributors to outline the rectums on the fused images (planning and verification scans)

• Collation of data and statistical analysis

1. De Crevoisier, R., Tucker, S.L., Dong, Mohan, R., Cheung, R., Cox, J.D., et al., Increased risk of biochemical and local failure in patients with distended rectum on the planning CT for prostate cancer radiotherapy. Int. J. Radiation Oncology Biol. Phys., 2005. 62(4): p. 965-973.

2. Pinkawa M, Siluschek J, Gagel B, et al. Influence of the initial rectal distension on posterior margins in primary and postoperative radiotherapy for prostate cancer. Radiother Oncol 2006; 81:284–290.

3. Zelefsky, M., Crean, D. and Mageras, G., Quantification and predictors of prostate position variability in 50 patients evaluated with multiple CT scans during conformal radiotherapy. Radiotherapy and Oncology, 1999. 50: p. 225-234.

4. Beard, C., Kijewski, P. and Bussiere, M., Analysis of prostate and seminal vesicle motion: Implications for treatment planning. Int J Radiat Oncol Biol Phys, 1996. 34: p. 451- 458.

5. Fiorino C ; Di Muzio N ; Broggi S ; Cozzarini C ; Maggiulli E ; Alongi F ; Valdagni R ; Fazio F ; Calandrino R et al .Evidence of Limited Motion of the Prostate by Carefully Emptying the Rectum as Assessed by Daily MVCT Image Guidance with Helical Tomotherapy. International Journal of Radiation Oncology, Biology, Physics, 2008, Vol.71 (2), p.611-618.

Dr S Yahya