Absorbable Hydrogel Spacer Use in Prostate Radiotherapy: A Comprehensive Review of Phase 3 Clinical Trial Published Data

Abstract

To provide an update on SpaceOAR System, a Food and Drug Administration-approved hydrogel indicated to create distance between the prostate and the rectum which has been studied in phase 2 and 3 clinical trials. Here, we review and summarize these clinical results including the safety of prostate-rectum spacer application technique, the implant quality and resulting rectal dose reduction, acute and long-term rectal, urinary, and sexual toxicity, as well as patient-reported outcomes. A prospective, randomized patient-blinded clinical study was performed comparing image-guided intensity modulated prostate radiotherapy (79.2 Gy in 44 fractions) in men with or without prostate-rectum hydrogel spacer. Patients were followed up for 3 years, allowing assessment of long-term safety and efficacy. Spacer application was well tolerated with a 99% technical success rate. The mean additional space created between the prostate and the rectum was just over 1 cm, which allowed significant rectum and penile bulb radiation dose reduction, resulting in less acute pain, lower rates of late rectal toxicity, and improved bowel and urinary quality of life (QOL) scores from 6 months onward. Improvements in sexual QOL were also observed at 37 months in baseline-potent men, with 37.5% of control and 66.7% of spacer men capable of "erections sufficient for intercourse." Prostate-rectum hydrogel spacer application is a relatively safe technical procedure that is well tolerated and has a high technical success rate. Spacer application significantly reduces rectal radiation dose and results in long-term reductions in rectal toxicity, as well as improvements in bowel, urinary, and sexual QOL.