SpaceOAR Hydrogel Spacer for Reducing Radiation Toxicity During Radiotherapy for Prostate Cancer. A Systematic Review.

Objective: To evaluate the association between SpaceOAR and radiation dosing, toxicity and quality-of-life vs no spacer across all radiotherapy modalities for prostate cancer.

Methods: A systematic search of the Cochrane Central Register of Controlled Trials, MEDLINE, and Embase was performed from database inception through May 2020. Two reviewers independently screened titles/abstracts and full papers. Data extraction was performed, and quality assessed by 1 reviewer and checked by a second, using a third reviewer as required. The synthesis was narrative.

Results: 19 studies (3,622 patients) were included (only 1 randomized controlled trial, in image-guided intensity-modulated radiotherapy (IG-IMRT), 18 comparatives non-randomized controlled trials in external-beam radiotherapy (EBRT), brachytherapy, and combinations thereof). No hypofractionation studies were found. Regardless of radiotherapy type, SpaceOAR significantly reduced rectal radiation dose (eg, V40 average difference -6.1% in high dose-rate brachytherapy plus IG-IMRT to -9.1% in IG-IMRT) and reduced gastrointestinal and genitourinary toxicities (eg, late gastrointestinal toxicity 1% vs 6% (P = .01), late genitourinary toxicity of 15% vs 32% (P < .001) in stereotactic body radiotherapy). Improvements were observed in most Expanded Prostate Cancer Index Composite quality-of-life domains (eg, bowel function score decrease at 3 and 6 months: Average change of zero vs -6.25 and -3.57 respectively in low dose-rate brachytherapy plus EBRT).

Conclusion: The randomized controlled trial in IG-IMRT demonstrated that SpaceOAR reduces rectal radiation dose and late gastrointestinal and genitourinary toxicities, with urinary, bowel, and sexual quality-of-life improvement. These advantages were verified in observational studies in various radiotherapy types. Further research is required in hypofractionation.