Introduction: SpaceOAR is a hydrogel spacer introduced to reduce rectal radiation dose, toxicity, and complications (bowel, urinary, and sexual) for prostate cancer patients undergoing radiation therapy (RTx). Yet, SpaceOAR placement outcomes in the salvage radiation population remain to be established. We aim to investigate the outcomes and complications associated with SpaceOAR placement in patients undergoing salvage RTx. Methods: We reviewed our institutional Radiation Oncology database for patients undergoing salvage RTx from 01/2018 – 05/2022. We identified patients who had an attempted SpaceOAR placement and assessed success rate as well as complications associated with the placement and subsequent RTx. We tested associations using the statistical t-test, with p-values <0.05 considered statistically significant. Results: We identified 36 patients who underwent salvage high dose-rate brachytherapy. 22 patients had an attempted SpaceOAR placement prior to salvage RTx, of which 20 (90.1%) were successful. All SpaceOAR placements were performed in the operating room. The two unsuccessful SpaceOAR placements were aborted due to 1) diffusion along the anterior rectal wall and 2) inadequate hydro-dissection due to encountering dense fibrotic tissue. The average interval between SpaceOAR placement and prior RTx was 112 months (±46 months). No patients developed an acute complication that prevented them from receiving their scheduled salvage radiation therapy. Of the patients that underwent attempted SpaceOAR placement and then completed salvage RTx, five reported uncomplicated hematuria (22.7%), one developed a recto-urethral fistula (4.5%), two experienced acute urinary retention (9.1%), and one reported pain (4.5%). Conclusions: Here we present the first series of patients in the salvage radiation setting undergoing SpaceOAR placement. In well selected patients, SpaceOAR hydrogel placement is safe in the setting of salvage radiation therapy. Hydrogel placement was successful in over 90% of the patients who had an attempted placement. No post-procedure complications occurred that delayed or prevented salvage treatment. SOURCE OF Funding: None
