Patient-Reported Outcomes With Stereotactic Intensity Modulated Radiotherapy After Radical Prostatectomy

Importance Postoperative radiotherapy remains underused for men with biochemical recurrence or adverse pathological features after radical prostatectomy (RP). Stereotactic body radiotherapy (SBRT) may improve utilization and poses potential radiobiological advantages. Objective To evaluate physician-reported late toxic effects and 2-year patient-reported outcomes (PROs) following post-RP SBRT. Design, Setting, and Participants This phase 2, single-arm trial was conducted in 2 academic centers in the US and included a comparator cohort. Men with post-RP prostate-specific antigen greater than 0.03 ng/mL or adverse pathologic features were included. Data were collected from February 2018 to March 2021, and data were analyzed from January to October 2024. Interventions SBRT delivered at 30 to 34 Gy in 5 fractions to the prostate bed. Nodal irradiation, boost to gross disease, and/or hormonal therapy were delivered per physician discretion. Main Outcomes and Measures Late toxic effects (more than 90 days after treatment) were graded according to Common Terminology Criteria for Adverse Events version 4.03. PROs were measured using Expanded Prostate Cancer Index-26. The proportion of men whose PROs had decrements greater than twice the threshold for minimal clinically important difference (MCID) at any point during the first 2 years were evaluated. The longitudinal PROs for men receiving SBRT was compared with a cohort of 200 men receiving postoperative conventionally fractionated radiotherapy (CFRT) using logistic regression, while adjusting for baseline scores, age, and receipt of nodal irradiation. Results Of 100 patients treated with post-RP SBRT, the median (IQR) age was 68.5 (63.9-71.4) years, and the median (IQR) follow-up was 43 (37-53) months. Cumulative incidence of late grade 2 and 3 genitourinary toxic effects was 25% and 4%, respectively, and of late grade 2 and 3 gastrointestinal tract toxic effects was 3% and 3%, respectively. The proportion of patients with decrements more than 2-fold the MCID in PROs was 38.9% (37 of 95) for urinary incontinence, 17.9% (17 of 95) for urinary irritation, and 34.1% (31 of 91) for bowel function. Compared with the CFRT cohort, the adjusted odds ratio for patients receiving SBRT experiencing decrements more than 2-fold the MCID was 1.55 (95% CI, 0.87-2.76; P = .14) for urinary incontinence, 0.94 (95% CI, 0.46-1.94; P = .87) for urinary irritation, and 1.03 (95% CI, 0.57-1.84; P = .93) for bowel function. Conclusions and Relevance In this nonrandomized clinical trial, post-RP SBRT was well-tolerated, with no measurably different decline in urinary or bowel PROs through 2 years compared with CFRT. Randomized studies and longer follow-up will better define the toxic effects and efficacy profile of post-RP SBRT. Trial Registration ClinicalTrials.gov Identifier: NCT03541850