Effectiveness of Rectal Retractor in Radiotherapy for Prostate Cancer: A Review

Prostate cancer is one of the most common malignant diseases among males. External beam radiation therapy (EBRT) is one of the major curative treatment modality for the localized prostate cancer. High-dose radiotherapy for localized prostate cancer is a well-established method to improve tumor control but is also resulted in increased rectal toxicity. Major concern of dose escalation in prostate cancer is the toxicity of surrounding normal tissues, in particular rectum because the rectum is anatomically close to the prostate gland and limits prescribed dose. Radiotherapy associated rectal toxicities have a negative impact on patient’s quality of life (QOL). The primary efforts for reduction of rectal toxicities are the application of image guided radiation therapy (IGRT), intensity modulated radiation therapy (IMRT) or adaptive radiotherapy. However, the part of the rectum receives high doses even with modern radiotherapy techniques. Hence, physical displacement of the rectum from the prostate can be effective in reducing rectal radiation doses. To date, three different rectal displacement devices such as Endorectal balloons (ERBs), tissue hydrogel spacers, and rectal retractor (RR) have been developed to push the rectal wall away from the prostate. Previously, the effectiveness of ERBs and tissue hydrogel spacers has been widely investigated. A RR, as a novel device, inserted into the rectum can be utilized to push the rectal wall away from high-dose regions and potentially reduce radiotherapy-induced rectal toxicity. Regarding RR, conflicting reports in the literature debate its efficacy in prostate cancer EBRT. Therefore, the aim of this review is to evaluate the effect of RR during prostate cancer external beam brachytherapy with regard to dosimetric results, preliminary clinical outcomes, prostate motion, and procedure-related toxicity.
To have a comprehensive study, we searched PubMed, Scopus, and Google Scholar studies from January 1th, 2010 to September 30th, 2022. The following keywords were used for the searches: rectal retractor, Rectafix, rectal displacement device, and synonyms combined with one or more of the following: prostate radiotherapy and prostate cancer radiotherapy. Reference lists of articles were also reviewed for relevant articles. Published articles and abstracts in English from preclinical and clinical studies were included. Fifteen articles were included in this review.
No serious complications such as severe anal irritation or rectal bleeding occurred with daily insertion of the RR. The magnitude of rectal retraction is determined by patient's discomfort. Although the rectal retraction induces a mild rectal pain, it is well tolerated. Daily use of the RR can lead to anorectal irritation, thus the RR cannot be used during the entire treatment sessions with the conventional radiation therapy regimen (more than 35 sessions). All of these events were self-limited and resolved with no additional treatment during radiotherapy. The insertion of the RR required approximately 3-4 additional minutes of routine set-up time. The application of RR can increase the space between the prostate and the anterior rectal wall. Using RR achieved the average distance of 4 mm between the prostate and the anterior rectal wall. The RR usage resulted in significant radiation dose reductions to the rectal wall, posterior rectal wall, and anterior rectal wall. Preliminary clinical data showed that using RR does not reduce acute rectal toxicities, but the rate of late rectal toxicities is lower in patients treated with a RR in-place. The RR can reduce prostate intra-fractional motion. Several reports indicated that in vivo rectal dosimetry was feasible using RR equipped with different active or passive dosimeters during prostate radiotherapy.
The use of RR for patients undergoing EBRT for prostate cancer was feasible and it did not lead to serious complications such as rectal bleeding. Using RR in definitive prostate EBRT resulted in reducing dose to the rectal wall. The RR can increase prostate and rectal inter- and intra-fractional stability. However, further randomized clinical trial with a large sample size will be required to clear the clinical benefits of the application of the RR during prostate radiotherapy.