Radiation proctitis after iodine-125 low-dose-rate prostate brachytherapy utilizing SpaceOAR hydrogel.

Objective: We retrospectively evaluated the efficacy of combining the SpaceOAR (SOAR) hydrogel with prostate brachytherapy, using colonoscopy findings to assess for radiation proctitis.

Methods: Among 731 patients undergoing iodine-125 low-dose-rate prostate brachytherapy (LDR-BT), SOAR was utilized in 394 patients (53.9%). Colonoscopy was performed for 97 patients (13.3%) to assess the presence, location, condition, and treatment of radiation proctitis. We also investigated treatment factors associated with the occurrence of radiation proctitis.

Results: Radiation proctitis was observed in 57 patients (7.8%) and 17 (2.3%) were treated with argon plasma coagulation (APC). The incidence of radiation proctitis was 12.2% in the non-SOAR and 4.1% in the SOAR group (p < 0.001). In the non-SOAR group, the incidence of radiation proctitis was 6.6% for LDR-BT monotherapy and increased to 22.0% when combined with external beam radiation therapy (EBRT) (p = 0.001). However, in the SOAR group, these rates significantly decreased to 3.3% and 5.7% for monotherapy and combination therapy, respectively (p = 0.035, p < 0.001). With SOAR, inflammation was observed directly above the DL in most patients (87.5%), and only one patient (6.3%) required APC. The absence of SOAR (p < 0.001, HR = 0.29) and the concurrent use of EBRT (p = 0.018, HR = 2.87) were identified as significant risk factors for the occurrence of radiation proctitis.

Conclusion: The use of SOAR significantly reduced the incidence of radiation proctitis in patients undergoing LDR-BT monotherapy and combined EBRT. Inflammation primarily occurred directly above the DL; further examination is necessary to clarify its cause.