Factors Associated With Rectal Spacer Use in Prostate Cancer Patients Receiving Radiation Therapy

Prostate cancer is a leading cause of cancer-related death among men in the United States. However, the influence of demographic, socioeconomic, regional, and treatment-related factors on rectal spacer use among men treated with radiation therapy remains largely unexplored in the literature. This study evaluated rectal spacer utilization among Medicare beneficiaries with prostate cancer by radiation therapy modality, region, race, income, and year.

The Medicare 5% Standard Analytical Files were used to identify men aged 65+ with prostate cancer who underwent treatment with intensity-modulated radiotherapy (IMRT), stereotactic body radiation (SBRT), brachytherapy, or proton therapy from 1/1/2017-12/31/2021. Patients were stratified by rectal spacer placement within 60 days pre-radiation therapy initiation.

A total of 66,680 patients were identified (mean age 72.8 years, mean Charlson Comorbidity Index score 3.26, 80.7% White). Among this cohort, 17,940 patients (26.9%) received a rectal spacer. Spacer utilization increased significantly over time, from 6.8% in 2017 to 42.4% in 2021 (p < 0.05). Geographic variation was observed, with the highest utilization in the West (31.7%) and the lowest in the Northeast (23.6%). A greater proportion of White patients received rectal spacers than Black patients in all regions except the Northeast (West: 32.6% vs. 22.2%; South: 30.8% vs. 20.5%; Midwest: 24.4% vs. 15.5%; all p < 0.001), where the opposite was observed (31.8% vs. 22.2%; p < 0.001). Rectal spacer utilization increased with income, ranging from 20.9% in the lowest income quintile to 28.2% in the highest (p < 0.001). By treatment modality, utilization was highest among patients receiving proton therapy (59.0%), followed by SBRT (46.0%), brachytherapy (23.7%), and IMRT (20.6%).

Rectal spacer utilization increased significantly from 2017 to 2021, with the greatest relative increases among proton therapy patients and SBRT patients. Significant variations based on geographic region, race, and income highlight the complex interplay of these factors on treatment access and decision-making.