SpaceOAR hydrogel complications in prostate cancer radiotherapy: a pictorial review

Since its approval by the United States Food and Drug Administration (FDA), the rectal hydrogel spacer system SpaceOAR (SpaceOAR™ and Space-OAR Vue™, Boston Scientific Corporation, Marlborough, Massachusetts, United States) has become widely adopted in radiation therapy protocols for prostate cancer patients. The biodegradable hydrogel creates a temporary space between the prostate and rectum, thereby effectively reducing the radiation exposure to the anterior rectal wall. While the system is generally safe, potential complications can occur and should be recognized by radiologists. This pictorial review aims to familiarize radiologists with imaging features of SpaceOAR-related complications to ensure accurate diagnosis and reporting.