Impact of double-balloon rectal catheter use in external-beam radiotherapy for prostate cancer

Abstract

Prostate motion and rectal sparing are important treatment strategy issues in external-beam radiotherapy for localized prostate cancer. To address these issues, we prospectively investigated the feasibility of using a double-balloon rectal catheter. The rectal catheter has inner and outer balloons that wedge the anus between them. Computed tomography (CT) examinations with and without the catheter were conducted in seven patients with localized prostate cancer treated by external-beam radiotherapy. The rectal wall sparing effect was evaluated using virtual three-dimensional conformal radiotherapy plans in each arm. To evaluate interfractional prostate motion, each patient underwent a series of four CT examinations consisting of a planning CT followed by three additional series of CT with and without a catheter during the course of radiotherapy. Virtual plans demonstrated the reduction of the dose to the rectum by expanding the posterior wall to lie outside the high- to intermediate-dose area when a catheter was applied. Interfractional prostate motion in the anteroposterior direction was effectively reduced by catheter usage; the mean±standard deviation (SD) of the displacement was 1.3±0.9mm with a catheter as compared to 2.8±1.8mm without a catheter (P=0.014), and the maximum displacement was successfully suppressed to 3mm with a catheter compared to 6mm without a catheter. Systematic and random components were also reduced with the catheter. These results suggest the feasibility and clinical applicability of the double-balloon rectal catheter.