3659 - Examining Rectal Spacer Use in Prostate Cancer Radiation Therapy by Treatment Modality: Insights from Medicare Claims Data

R. Hankins¹, K. Morris², A. McGovern², S. P. Collins¹, and J. B. Yu³; ¹MedStar Georgetown University Hospital, Washington, DC, ²Boston Scientific, Marlborough, MA, ³Smilow Cancer Hospital, Hartford, CT

Purpose/Objective(s): A 2015 randomized controlled trial indicated improved clinical outcomes with rectal spacing prior to prostate radiotherapy, leading to regional Medicare Administrative Contractors approving coverage in 2017. Whether nationwide adoption has plateaued, peaked, and declined, or is entering the exponential phase of growth, remains an open question. This study investigated patterns of rectal spacer utilization by radiation therapy type among a nationally-representative sample of men with prostate cancer in the United States from 2017-2021. Materials/

Methods: The 100% Medicare Standard Analytical Files, which include hospital-based claims from all patients covered by fee-for-service Medicare, were used to identify men aged 65+ who received a prostate cancer diagnosis between January 1, 2017 and December 31, 2021. Eligible patients were required to have received either intensity-modulated radiotherapy, stereotactic body radiation (SBRT), brachytherapy, or proton therapy following their prostate cancer diagnosis. Patients were required to have continuous Medicare fee-for-service enrollment for at least 3 years pre- and 1-year post-radiation therapy index date. Men who received a radical prostatectomy within the 3-year pre-index period or who were diagnosed with any non-prostate cancer malignant neoplasm during the study period were excluded. Included patients were evaluated for the presence of a rectal spacer within 60 days prior to their radiation therapy index date.
Results: The proportion of patients receiving radiation therapy for prostate cancer (mean age: 73.1 years) who received a rectal spacer increased from 4% in 2017 to 28% in 2021, irrespective of radiation therapy type (p<0.05). This increase represented a compound annual growth rate (CAGR) of 2% per year. The most substantial increase was observed among patients receiving SBRT, increasing from 10% in 2017 to 47% in 2021 (CAGR: 16%). Racial identification was significantly associated with rectal spacer utilization, with a higher proportion of White identifying patients receiving rectal spacers compared to Black identifying patients across all radiation therapy types (18.5% vs. 13.1%, p<0.001), with the greatest percentage difference seen among patients who received SBRT (37.2% vs. 25.7%, p<0.001).
Conclusion: Rectal spacer utilization increased from 2017 to 2021 among prostate cancer patients receiving radiation therapy, with the most substantial increase observed among patients who received SBRT. Future research should evaluate potential disparities in rectal spacer utilization among various subgroups of prostate cancer patients.