To evaluate the efficacy of a Belly Board immobilisation device for rectal cancer patients.

A randomised trial in patients receiving neo-adjuvant chemoradiation for rectal carcinoma was established. Patients were treated, prone with control arm, according to standard departmental protocol and experimental arm with the use of a Belly Board. All treatments were planned using a three-field technique. The primary endpoints were reproducibility and irradiated small bowel volume. Questionnaires were used to assess secondary endpoints of patient comfort, ease of set-up and acute toxicities.

Pre-planned interim analysis was performed after recruiting 30 patients. In all, 348 portal images were analysed retrospectively. Around 8 out of 12 parameters measuring set-up reproducibility were in favour of the Belly Board arm. Random error in the anterior–posterior direction was improved and statistically significant in the experimental arm (95% CI; p≤0·05). Small bowel V15 was significantly lower in the Belly Board position (mean V15=14·5%) compared with the standard position (mean V15=21·4%), paired t-test 95% CI; p=0·035. Also, patients’ comfort satisfaction was greater in the Belly Board arm.

Set-up reproducibility, small bowel V15, patient comfort and satisfaction were all significantly improved by the use of the Belly Board.