OC-0414: Evaluating the role of a micro-enema to reduce rectal volume variation and gas during radiotherapy for bladder cancer

A feasibility study for the introduction of micro-enema to improve organ consistency in patients receiving radiotherapy for urinary bladder cancer

“…In this cohort study, we found a significant reduction in rectal volume variability resulting from gas and faeces following the introduction of micro-enema before planning and treatment ( p =<0·001). The control group result for rectal reproducibility is concordant with a previous audit that showed that 60% of fractions were delivered with a different rectal volume to that of the planning scan 20 . The study is limited by a small sample size, consecutive patient groups and non-matched treatment schedules (palliative and radical).…”

“…Diet as a method of managing rectal variation has been investigated with mixed results. [26][27][28][29] Looking to influence the rectal volume and the presence of gas with dietary advice proved unfeasible in our local, small group study of patients receiving bladder radiotherapy. In total, 80% of patients self-identified comorbidity that required them to follow a specific diet.…”

“…It was concluded from this limited review that generic dietary advice to influence rectal status in bladder cancer patients is largely ineffective and maybe inappropriate. [27][28][29] The use of a micro-enema before planning and treatment, in line with the local prostate radiotherapy protocol, was implemented and evaluated following local audit committee approval. The findings are presented.…”

“…, 19 Cone beam computed tomography (CBCT) is acquired immediately before treatment delivery to select the daily treatment plan whereby the planned target volume (PTV) is providing optimal bladder dose coverage. Adaptive techniques aim to facilitate increased treatment conformity and dose reduction to surrounding structures, 20 with reduced dose to OAR considered a major benefit of IGRT and adaptive radiotherapy 1 . The requirement for adaptive radiotherapy and the associated imaging is based on: The limitations of a ‘snap shot’ single planning scan that assumes reproducible anatomy for treatment. The inadequacy of bladder volume alone to reflect shape and position of the treated structure. The visualisation of three-dimensional images to facilitate matching. …”

“…In a recent, unpublished audit at the authors’ clinic, 20% of bladder volumes were 50 cc larger 20 at treatment than on the planning computed tomography (CT), which has been shown to correlate with a bladder wall displacement of up to 1 cm 21 22 This variation accounts for a significant proportion of a standard 1·5 cm elliptical margin, before any additional effect of shape deformity and intra-fraction motion are encountered.…”