Patient-reported Outcomes after Standard and Dose-escalated Prostate Stereotactic Body Radiotherapy.

AIMS: Dose escalation may improve tumor control in prostate stereotactic body radiotherapy (SBRT), but its impact on patient-reported outcomes (PROs) remains unclear. We evaluated urinary and bowel PROs after prostate SBRT, focusing on the impact of dose escalation. MATERIALS AND METHODS: This single-institution retrospective cohort study included consecutive patients treated with five-fraction prostate SBRT between 2016 and 2024. The primary outcomes were Expanded Prostate Cancer Index Composite (EPIC) urinary irritative/obstructive (EPIC-UIR) and bowel (EPIC-B) scores. Patients with at least one EPIC-UIR or EPIC-B assessment within 36 months after treatment were included. Prescribed dose varied over time according to institutional clinical practice. Patients were categorized into a lower-dose group (≤40 Gy) and a higher-dose group (>40 Gy). Linear mixed-effects models were used to evaluate longitudinal trajectories. Clinically meaningful deterioration was assessed using minimal clinically important difference (MCID)-based analyses in the acute (1- and 3-month timepoints) and late (6- to 36-month timepoints) phases. RESULT: Among 940 patients treated with SBRT, 872 patients constituted the subjects of the PRO analysis, including 672 in the lower-dose group and 200 in the higher-dose group. In both groups, urinary and bowel scores showed acute decline followed by early recovery. Compared with the lower-dose group, the higher-dose group showed less favorable late urinary outcomes in both longitudinal analyses (P < .001) and MCID-based analyses, with late urinary worsening observed in 68% versus 80% of patients (P = .007). CONCLUSION: Dose escalation in prostate SBRT may involve a trade-off with late urinary PROs, highlighting the need for careful consideration of urinary organs at risk.