Association Between Rectal Spacer Use and Erectile Dysfunction Diagnosis Among Men Receiving Prostate Radiotherapy: US County-Level Analysis.

BACKGROUND: Rectal spacers have been shown in clinical studies to reduce side effects of radiotherapy (RT) in prostate cancer (PCa) patients. In addition, secondary analyses also showed reduced erectile dysfunction following PCa RT with the use of a rectal spacer. However, this association with erectile dysfunction (ED) in large-scale real-world settings remains unexplored. This study evaluated the association between rectal spacer use and the prevalence of ED diagnosis among PCa patients receiving prostate RT at the US county level. METHODS: This study utilized Medicare 5% and 100% Standard Analytic Files to analyze county-level data. The analytical sample included adult PCa patients receiving RT-comprising stereotactic body radiation therapy (SBRT), intensity-modulated radiation therapy (IMRT), proton beam radiation therapy, and brachytherapy-between January 2015 and March 2023. The primary outcome was the county-level proportion of RT patients diagnosed with ED between January 2015 and March 2023. The primary explanatory variable was the proportion of patients receiving prostate RT utilizing a rectal spacer from 1 to 5 years prior to an ED diagnosis. Zero-inflated Poisson regression models were used to assess the association between rectal spacer use and ED prevalence at the county level, controlling for county-level PCa patient characteristics (median age and racial composition) and general population characteristics (median age, racial composition, and median household income). State-level fixed effects accounted for regional variation. Data for general population characteristics were obtained from the 2020 Agency for Healthcare Research and Quality Social Determinants of Health Database. RESULTS: The study included 247,250 PCa patients who underwent RT across 3132 US counties between January 2015 and March 2023. The average annual prevalence of ED among PCa patients receiving RT at the county level was 1.3%. During the study period, the proportion of patients receiving rectal spacers increased from 2.9% to 18.9%. After adjusting for confounders, counties with higher rectal spacer use 4-5 years prior had a significantly lower prevalence of ED: a 10-percentage point increase in rectal spacer use at the county level was associated with a 7.7% relative reduction in ED prevalence after 4 years (p < 0.001) and an 8.4% reduction after 5 years (p = 0.006). CONCLUSION: This is the first large-scale real-world analysis to demonstrate an association between rectal spacer use and ED prevalence among PCa patients undergoing RT. County-level analysis suggests that increased use of rectal spacing among PCa patients receiving RT is associated with a significantly lower prevalence of ED, with benefits emerging after a 4-5-year time lag. These findings support the long-term benefit of rectal spacer use in preserving sexual function in PCa patients undergoing prostate RT. Future research should evaluate the etiology of the delayed benefit observed in this study.