The role of rectal sparing devices in post-prostatectomy radiotherapy: a review article

Adjuvant or salvage radiotherapy can control biochemical relapse after radical prostatectomy and reduce the risk of distant metastases. Dose-escalated radiotherapy after radical prostatectomy can lead to improved biochemical relapse-free survival. Over the last decades, despite the technological advancements in prostate radiotherapy, radiation-induced rectal toxicity is still the main limiting factor for dose escalation owing to the anatomical proximity of the prostate gland to the rectum. To this end, several rectal sparing devices, including Endorectal balloons (ERBs), prostate-rectum spacers (e.g. SpaceOAR hydrogel), and rectal retractor have been explored to increase the distance between the prostate and the rectum to reduce rectal radiation doses and toxicities. Over the last decade, several studies applied these devices during post-prostatectomy radiotherapy setting. Therefore, the purpose of this review is to evaluate the impact of rectal sparing devices on dose-volume parameters of anorectal, radiation-induced rectal toxicity, and prostate bed motion during post-prostatectomy radiotherapy. The results showed that although using ERBs can lead to stability in the target volume position, it cannot reduce rectal radiation doses, in particular dose to the anterior rectal wall. The application of ERBs can reduce the received dose of the anal wall and increase the geometric reproducibility of the clinical target volume (CTV) position. However, the role of ERBs in reducing the received dose of the rectal wall is still controversial, which can be associated with the displacement of the anterior rectal wall towards the prostate bed (high radiation dose area). The use of SpaceOAR hydrogel can significantly increase the distance between the rectum and the prostate bed and ultimately reduce the dose received by the rectal wall. Also, the use of rectal retractor remarkably reduces rectal radiation doses. The dosimetric and clinical results of the use of SpaceOAR hydrogel and rectal retractor are very promising, and these devices can be used for patients after the necessary evaluations by radiation oncologist in post-prostatectomy radiotherapy. However, further studies will be required to elucidate the efficacy of SpaceOAR hydrogel and rectal retractor in reducing radiotherapy-induced rectal toxicity following post-prostatectomy radiotherapy.