Association Between Perirectal Spacer Use and Short-Term Complications After Prostate Radiation Therapy in a National...

Perirectal spacers theoretically reduce radiation dose to the rectum and adjacent structures during prostate radiation therapy and may reduce genitourinary toxicity. However, large-scale studies evaluating clinical outcomes associated with spacer placement outside of clinical trial settings remain limited.

Using the Merative MarketScan Commercial and Medicare Databases, we identified individuals who underwent radiotherapy for prostate cancer from 2016 to 2022. Those who received a perirectal spacer before radiotherapy were compared with those who underwent radiotherapy without spacer placement. The primary outcomes were genitourinary and rectal toxicities within 12 months of treatment. Multivariable Cox proportional hazards models were constructed adjusting for age, comorbidity, insurance type, androgen deprivation therapy use, and radiotherapy modality. Twelve-month total health care costs were compared between groups.

Among 32,319 eligible patients, 5964 (18%) received a perirectal spacer. The perirectal spacer was associated with lower 1-year incidence and hazard of all-cause urinary toxicity (18.6% vs 21.5%, HR 0.88, 95% CI: 0.83-0.93, P < .01), urinary incontinence (13.8% vs 16.2%, HR 0.89, 95% CI: 0.83-0.95, P < .01), and urinary tract infections (5.6% vs 6.3%, HR 0.86, 95% CI 0.78-0.96, P < .01). Receipt of a perirectal spacer was not associated with significantly improved all-cause rectal toxicity (HR 0.94, 95% CI 0.87-1.01, P = .09). Twelve-month total health care costs were lower in the spacer group ($35,417 vs $43,514; P < .001).

In this large observational claims-based study, perirectal spacer use during prostate radiotherapy was associated with reduced short-term urinary toxicities and health care costs, but not with a statistically significant difference in rectal toxicity, the primary Food and Drug Administration-approved indication.