Rectal wall sparing effect of a rectal retractor in prostate intensity-modulated radiotherapy

Abstract

Purpose: The objective of the study was to evaluate the effectiveness of a rectal retractor (RR) designed to protect rectal tissue in intensity-modulated radiotherapy (IMRT) by pushing rectal wall (RW) away from the prostate. Materials and Methods: Twelve patients with localized prostate cancer were enrolled into this study. Patients underwent two computed tomography (CT) scans without and with RR. A prescription of 80 Gy in 40 fractions was planned on CT scans with and without RR. This study evaluates the ability of the RR in RW dose reduction, in particular reduction of the RW V 70Gy≥ 25% in comparison with the plan without RR dose-volume histograms were generated with and without RR. The patient's tolerance was assessed by patient-reported outcomes. Results: The planning target volume coverage was equal for both without and with RR (P = 0.155). The mean dose to the RW was statistically significantly lower for the plan with RR than that for the plan without RR, a mean reduction of 5.8 Gy (P = 0.003). Significant relative reductions in rectal dose-volume parameters whether in absolute volume (cc) or as a percentage of contoured RW were detected. A relative reduction more than 25% in RW V70Gy(%) in 100% of patients was achieved. The rectal retraction resulted in a significant increase in the prostate to the rectum space at the prostate midgland level, an absolute increase of 2.7 mm. The retraction of the rectum induced a mean (±standard deviation) pain score of 2.7 (±1.3) according to the visual analog score. Conclusion: The application of a RR showed a remarkable rectal sparing effect during prostate IMRT. This may lead to reduced acute and late rectal toxicities in prostate IMRT.

Rectal retractor in prostate radiotherapy: pros and cons

“…An interesting benefit of this device is that retraction of the rectum can significantly reduce the ARW doses [ 13 , 14 ]. When the RR retracts the rectum, the ARW is slightly displaced from the prostate, and also the rectal retraction changes rectal shape, consequently reducing the volume of the ARW receiving high doses of radiation.…”

“…When the RR retracts the rectum, the ARW is slightly displaced from the prostate, and also the rectal retraction changes rectal shape, consequently reducing the volume of the ARW receiving high doses of radiation. It has been seen that using a RR can increase the space between the clinical target volume (CTV) and the ARW on sagittal CT images [ 14 ]. Of note, assessment of the space between the posterior borders of the CTV and the ARW on sagittal CT images only may be biased by the low resolution of the CT scan compared to MRI; however, separating ARW from the prostate at different levels (i.e.…”

“…Hence, previous clinical studies applied daily insertion of RR during the cone-down 15–20 and 10 treatment fractions in conventionally fractionated and moderate hypofractionated RT, respectively [ 13 , 18 , 19 ]. In a study, patients treated with conventionally fractionated IMRT (80/2 Gy) and a RR in-place experienced a mild pain according to the visual analog score [ 14 ]. The mean pain score with RR was 2.7 [ 14 ].…”

“…In a study, patients treated with conventionally fractionated IMRT (80/2 Gy) and a RR in-place experienced a mild pain according to the visual analog score [ 14 ]. The mean pain score with RR was 2.7 [ 14 ]. As reported in studies, patients experienced some discomfort associated with daily insertion of RR owing to the rectal retraction, but it was well tolerable [ 13 , 14 , 18 ].…”

“…The mean pain score with RR was 2.7 [ 14 ]. As reported in studies, patients experienced some discomfort associated with daily insertion of RR owing to the rectal retraction, but it was well tolerable [ 13 , 14 , 18 ]. In the PROMETHEUS study, it has been reported that discomfort with RR was moderate in 35% and severe in 14% of men [ 27 ].…”