Achieving an empty rectum for prostate radiation therapy: comparison of two laxative treatment.

INTERVENTION: Randomised trial comparing the effectiveness of two types of laxation regimens in their ability to achieve an empty rectum during prostate radiation therapy. Group 1 will be prescribed 1 sachet Movicol Half (Macrogol 3350 6.563g) per day to be consumed orally in the evening. Prescription is as follows ‐ Use of Movicol half strength is commenced 7 days prior to attending for CT simulation. Once CT simulation is completed use of Movicol half strength is then ceased. ‐ Use of Movicol Half strength is recommenced 7 days prior to commencing treatment and is then consumed daily for 7 weeks until treatment is completed. Group 2 will be prescribed Metamucil (9 grams per day) consumed orally as 1 x 3 gram serve added to a 250ml glass of water at breakfast, lunch and dinner. The group will also be prescribed 1 x Nutralife Probiotic 50 supplement consumed orally per day. Prescription is as follows. ‐ Use of Metamucil is commenced 7 days prior to attending for CT simulation. Once CT simulation is completed use of Metamucil is then ceased. ‐ Use of Metamucil is recommenced 7 days prior to commencing treatment and is then consumed daily for 7 weeks until treatment is completed. Compliance will be checked by completion of medication diary for the laxatives and through packet return for the probiotic. CONDITION: Prostate cancer PRIMARY OUTCOME: Differences in rectal gas measurements between the two treatment arms, ; Rectal gas which will be estimated by viewing the CT scan in the mid‐sagittal plane and using a semi quantitative scale of 1‐5; representing (1)no gas present, (2) gas occupying 5 to less than 25%, (3) 25 t less than 50%, (4) 50 less than 75% and (5) 75 less than 100% of the rectum. Differences in rectal volume between the two treatment arms, ; CT scans are routinely conducted during treatment with a total of 12 collected over the treatment period. Rectal volume will be measured by outlining the prostate, bladder and rectum on all CBCT scans. The rectal volume and cross sectional area will be recorded from this data SECONDARY OUTCOME: The number of patients with symptoms of diarrhoea during treatment requiring the cessation of laxatives. This will be assessed at weekly review appointments using the patient self‐reported diary which includes the Bristol stool chart. INCLUSION CRITERIA: Adult patients fifty years of age or older undergoing external bean radiotherapy (EBRT) to the intact prostate, using fiducial markers for position verification.