Real-world U.S. county-level analysis of erectile dysfunction diagnosis following radiation therapy for localized prostate cancer: The impact of rectal spacer utilization.

365 Background: Rectal spacers have been shown to reduce side effects of prostate radiotherapy (RT) in prostate cancer (PCa) patients in clinical studies. While rectal spacing may help preserve sexual function after RT, this association has not been explored in large-scale real-world data. This study evaluated the association between rectal spacer use and the prevalence of erectile dysfunction diagnosis among PCa patients receiving prostate RT at the U.S. county level. Methods: This study utilized Medicare 5% and 100% Standard Analytic Files to analyze county-level data. The population consisted of adult PCa patients receiving RT (IMRT, brachytherapy, SBRT, or proton therapy) between 2015 and 2022. The primary outcome was the county-level proportion of patients diagnosed with erectile dysfunction in any year between 2016 and 2023. The primary explanatory variable was the proportion of patients treated with RT using rectal spacer 1 to 5 years before erectile dysfunction diagnosis. Zero-inflated Poisson regression models assessed the association between rectal spacer use and erectile dysfunction diagnosis at county level, controlling for county-level PCa patients characteristics (average age and racial composition) and general population characteristics (median age, racial composition, and median household income). State-level fixed accounted for regional variation. Data for the general population were obtained from the Agency for Healthcare Research and Quality Social Determinants of Health Database 2020. Results: The study included 247,250 PCa patients receiving prostate RT during the study period across 3,132 U.S. counties. The average annual prevalence of erectile dysfunction diagnosis among PCa patients receiving RT at the county level was 1.3%. The proportion of patients receiving rectal spacers increased from 2.9% to 18.9% over the study period. After adjusting for confounders, counties with higher rectal spacer use 4-5 years prior had a significantly lower prevalence of erectile dysfunction diagnosis. A 10-percentage point increase in rectal spacer usage at the county level was associated with a 7.7% reduction in erectile dysfunction diagnosis after 4 years (p<0.001) and an 8.4% reduction after 5 years (p=0.006). Conclusions: In this first assessment of a real-world dataset, the county-level analysis suggests that increased use of rectal spacing among PCa patients receiving prostate RT is associated with a significantly lower prevalence of erectile dysfunction, with a time lag of 4 to 5 years. This finding supports the long-term benefit of rectal spacing in preserving sexual function in PCa patients undergoing prostate RT. Future research should evaluate the etiology of the longer than expected time lag between utilization and benefit.