Association of Perirectal Hydrogel Spacer Placement with Clinical Outcomes in Patients with Prostate Cancer Undergoing Radiotherapy: A Systematic Review and Meta-Analysis.

Purpose: To assess the relationship between perirectal hydrogel spacer placement and the clinical outcomes in men undergoing radiotherapy (RT) for prostate cancer.

Materials and methods: An extensive literature review was conducted using the PubMed/Medline, Embase, Cochrane Library, and Web of Science databases, encompassing studies published through June 2024. Group comparisons were performed using the weighted mean difference for continuous variables and the risk ratio for dichotomous measures. The primary endpoint was to compare rectal radiation doses with or without a perirectal spacer. Secondary outcomes included gastrointestinal (GI) and genitourinary (GU) toxicities (acute/late and any/grade ≥2, with subgroup analyses for hypofractionated RT.

Results: We reviewed 35 studies comprising 4,664 males. Rectal spacers effectively reduced the mean and maximum rectal radiation exposure, with reductions of 51.8% in V50 (mL) and 56.8% in V70 (mL). Furthermore, the percentage-based analysis showed reductions of 54.5% in V50 (%) and 62.2% in V70 (%). Acute GU toxicities (any grade and grade ≥2) showed no significant difference between the spacer and no-spacer groups, with no subgroup differences by fractionation. Late GU toxicities (any grade) were lower in the spacer group, while grade ≥2 toxicities showed no difference. Acute GI toxicities (any grade) were significantly reduced with spacers, particularly in hypofractionated RT, while grade ≥2 toxicities showed no difference. Late GI toxicities (any grade) were lower in the spacer group, with a stronger protective effect in hypofractionated RT. No significant difference was observed in grade ≥2 late GI toxicities.

Conclusions: Hydrogel spacers significantly reduced rectal radiation exposure and overall GI toxicity. However, their limited impact on severe toxicity highlights the need for further research on high-risk treatments and advanced RT techniques.