This OAR that.

Placement of SpaceOAR hydrogel between the prostate and rectum is touted, by SpaceOAR, as making an extremely safe prostate radiation treatment even safer. This commentary is here to ask: does it, really? The authors point out that the randomized trial assessing its efficacy didn’t actually meet its primary endpoint of demonstrating a benefit in grade 1+ rectal (plus procedural) adverse events. Instead, the SpaceOAR-funded paper concentrates on secondary analyses revealing improvement in grade 1-2 GI and even grade 1 GU events. What’s more, physicians weren’t blinded to treatment arms leaving, shall we say, space for observer bias—an especially intriguing possibility given there’s no dosimetric reason GU events should be affected by posterior displacement of the rectum. Add to that the 59 SpaceOAR-related grade 3+ toxicity events reported over a 5-year period in the FDA MAUDE database. TBL: “Critical reflection and careful consideration of the need, toxicity, and benefits of SpaceOAR are appropriate before the device is recommended for routine care.” | Hall, Lancet Oncol 2021