Polyethylene glycol-based hydrogel rectal spacers for prostate brachytherapy: a systematic review with a focus on technique

Abstract

Introduction Radiation dose to the rectum in prostate brachytherapy (PBT) can be reduced by the use of polyethylene glycol (PEG) hydrogel spacers. This reduces the rate of rectal toxicity and allows dose escalation to the prostate. Our objectives were to provide an overview of technique for injection of a PEG hydrogel spacer, reduction in rectal dosimetry, gastrointestinal toxicity and potential complications. Methods We systematically reviewed the role of PEG hydrogel spacers in PBT using the Cochrane and PRISMA methodology for all English-language articles from January 2013 to December 2019. Data was extracted for type of radiotherapy, number of patients, type of PEG-hydrogel used, mean prostate-rectum separation, rectal dosimetry, acute and late GI toxicity, procedure-related complications and the technique used for hydrogel insertion. Results Nine studies (671 patients and 537 controls) met our inclusion criteria. Of these 4 used DuraSeal ® and 5 used SpaceOAR ®. The rectal spacing achieved varied between 7.7-16 mm. Failure of hydrogel insertion was seen only in 12 patients, mostly related to failure of hydrodissection in patients undergoing salvage PBT. Where reported, the rectal D2 cc was reduced by between 21.6 and 52.6% and the median rectal V75% cc was reduced by between 91.8-100%. Acute GI complications were mostly limited to grade 1 or 2 toxicity (n = 153, 33.7%) with low levels of grade 3 or 4 toxicity (n = 1, 0.22%). Procedure-related complications were limited to tenesmus (0.14%), rectal discomfort (1.19%), and bacterial prostatitis (0.44%). Conclusions PEG hydrogel spacers are safe to insert. Gel insertion is easy, fast and has a low rate of failure. These studies convincingly demonstrate a significant reduction in rectal dosimetry. Although the results of spacers in reducing rectal toxicity is promising, these need to be confirmed in prospective randomised trial.

Use of a Biodegradable, Contrast-Filled Rectal Spacer Balloon in Intensity-Modulated Radiotherapy for Intermediate-Risk Prostate Cancer Patients: Dosimetric Gains in the BioPro-RCMI-1505 Study

“…polyethylene glycol (PEG)] into the perirectal fat. Indeed, the use of spacers is associated with less rectal AEs ( 9 – 11 ). By way of an example, 222 patients with stage T1 or T2 prostate cancer and undergoing image-guided IMRT (79.2 Gy in 1.8-Gy fractions) were randomized to spacer implantation or no implantation ( 12 , 13 ).…”

Rectal spacers in patients with prostate cancer undergoing radiotherapy: A survey of UK uro‐oncologists

“…In the phase III study, almost all investigators rated the injection of SpaceOAR as easy or very easy, so this would not be expected as a barrier to more widespread use 15 . Additionally, studies have shown that acute rectal toxicity associated with hydrogel spacers is very uncommon (<2% of patients), 22 although patients may experience rectal discomfort prior to spacer hydrolysis 17,23 …”

“…(<2% of patients), 22 although patients may experience rectal discomfort prior to spacer hydrolysis. 17,23 The other major subgroup where the uro-oncologists would currently consider rectal spacers were those with pre-existing bowel conditions or those considered to be at higher risk of bowel toxicity. It is known that individuals with prostate cancer and inflammatory bowel disease experience an increased rate of adverse effects of radiotherapy, in particular EBRT, although to a lesser extent with brachytherapy.…”

FEMOSSA: Patient‐specific finite element simulation of the prostate–rectum spacer placement, a predictive model for prostate cancer radiotherapy

“…Secondly, a misplaced injection can increase the chance of infection, inflammation, and rectal wall infiltration. Further, rectal ulcer and wall erosion, prostatic abscess and sepsis, recto‐urethral fistula, and purulent perineal drainage were reported in some cases, 16–18 whereas another study showed that the mislocated spacer decreases the level of rectal dose reduction 19 . Finally, although the injection of more hydrogel, and therefore, more separation is appealing from the dosimetric viewpoint, it is associated with a higher chance of procedure failure.…”