Bowel Disorder Incidence and Rectal Spacer Use in Patients With Prostate Cancer Undergoing Radiotherapy.

Importance: The polyethylene glycol-based hydrogel spacer (PHS) system temporarily separates the rectum from the prostate in patients undergoing radiotherapy (RT) for prostate cancer (PCa). Objective: To compare incidence of bowel disorders and related procedures in patients receiving RT with and without PHS. Design, Setting, and Participants: This retrospective cohort study used 4 datasets: Medicare 5% Standard Analytic Files, Medicare 100% Standard Analytic Files, Merative MarketScan Commercial Database, and Premier Healthcare Database. Participants included adult patients with PCa undergoing RT from 2015 to 2021. Exposure: Placement of PHS. Main Outcomes: All-cause bowel disorders and related procedures, identified from diagnosis and procedure codes. Results were compared with age-matched male general population without PCa or RT. Results: Of 261 906 patients with PCa included in the study, 25 167 (9.6%) received PHS (mean [SD] age, 70.7 [6.5] years) and 236 739 did not (mean [SD] age, 71.1 [7.5] years). One year prior to RT, patients who received PHS had a lower mean (SD) Charlson Comorbidity Index score than those who did not (2.48 [1.08] vs 3.14 [1.95]; P < .001). Stereotactic RT was more common in patients who received PHS (2743 [10.9%] vs 8810 [3.7%]; P < .001), while intensity-modulated RT was less common (12 755 [50.7%] vs 142 402 [60.2%]; P < .001). After 4 years post RT, patients who received PHS had a 25% lower hazard of bowel disorders (hazard ratio [HR], 0.75 [95% CI, 0.72-0.78]; P < .001) and a 46% lower hazard of related procedures (HR, 0.54 [95% CI, 0.47-0.62]; P < .001) than patients who did not receive PHS. Patients without PHS had higher hazard compared with an age-matched general population (disorders: 17.1% [95% CI, 17.3%-17.6%] vs 10.3% [95% CI, 10.1%-10.5%]; HR, 1.35 [95% CI, 1.32-1.37]; P < .001; procedures: 2.0% [95% CI, 1.9%-2.1%] vs 0.7% [95% CI, 0.7%-0.8%]; HR, 1.92 [95% CI, 1.79-2.06]; P < .001), while patients who received PHS did not (disorders: 12.4% vs 10.3%; HR, 1.00 [95% CI, 0.98-1.05]; P = .82; procedures: 1.1% [95% CI, 1.0%-1.3%] vs 0.7% [95% CI, 0.7%-0.8%]; HR, 1.11 [95% CI, 0.96-1.29]; P = .15). Common procedures included colonoscopy, sigmoidoscopy, and rectal resection. Conclusions and Relevance: In this cohort study of patients with PCa receiving RT, those receiving a PHS had a significantly lower incidence of all-cause bowel disorders and related procedures compared with patients who did not receive a PHS over the 4-year follow-up. The incidence among patients with PHS was similar to the general population. These findings are consistent with prior phase 3 trial results, where patients receiving PHS experienced no decline in bowel quality of life.