Robot-Assisted Laparoscopic Radical Prostatectomy 6 Months After Rectal Spacer Hydrogel Injection

SpaceOAR (organ at risk) hydrogel is a hydrogel matrix injected into the perirectal space posterior to the prostate for the purpose of mitigating radiation dose (and hence side effects of radiation) on the rectum. Manufacturer descriptions state that this material is reabsorbed 3 to 6 months after injection. We encountered a 75-year old male patient who underwent SpaceOAR injection in anticipation for primary external beam radiation treatment for intermediate risk prostate cancer (Gleason score 7 = 4 + 3, prostate specific Antigen [PSA] = 2.32, cT2a). After initiation of androgen deprivation, but before radiotherapy, the patient decided to no longer undergo radiation but rather elected to proceed with surgery. Based on the presence of the SpaceOAR, we delayed his surgery to 6 months after SpaceOAR injection to allow for absorption of the material. A preoperative MRI showed persistent hydrogel matrix in the perirectal space. We performed a robotic radical prostatectomy effectively despite the persistent SpaceOAR hydrogel by modifying our dissection closer to the prostate posteriorly. SpaceOAR hydrogel may alter patient anatomy even 6 months after deployment, however, robotic prostatectomy would be feasible with proper knowledge of anatomy and by following the proper dissection planes above the perirectal space.