Sep 29

SS 29 - Intensify, Shorten, or Personalize? Modern Approaches to Post-prostatectomy RT

252 - Postoperative Stereotactic Body Radiotherapy (SBRT) to the Prostate Bed for Biochemical Recurrence: Results from the Prospective Multicenter POPART Trial

01:00pm - 01:10pm ET

Room 210

Presenter(s)

Denis Panizza, MSc - University of Milan Bicocca, Monza, Lombardia

F. Ferrario¹, V. Faccenda², D. Panizza³, M. Mombelli³, I. Manno³, S. Saufi³, R. R. Colciago⁴, V. Pisoni¹, E. De Ponti³, and S. Arcangeli³; ¹Fondazione IRCCSA San Gerardo dei Tintori, Monza, Italy, ²Fondazione IRCCS San Gerardo dei Tintori - Medical Physics, Monza, Italy, ³University of Milan Bicocca, Milan, Italy, ⁴Universita degli Studi di Milano - Bicocca, Milan, Lombardia, Italy

Purpose/Objective(s):

Biochemical recurrence (BCR) occurs in up to 50% of patients within five years after radical prostatectomy. Salvage normofractionated radiotherapy is the standard treatment, although ultra-hypofractionated approaches such as stereotactic body radiotherapy (SBRT) may improve treatment efficiency and patient convenience. However, prospective data on postoperative SBRT to the prostate bed are limited. The multicentric POPART trial was designed to prospectively assess the incidence and predictors of grade =2 late genitourinary (GU) adverse events (AEs) following prostate-bed SBRT, and to characterize associated longitudinal changes in patient-reported outcomes (PROs) and biochemical recurrence-free survival (BRFS).

Materials/Methods:

POPART is a prospective multicenter study investigating SBRT delivered as 32.5 Gy in five alternate-day fractions on a Linac platform. Eligible patients had histologically confirmed prostate cancer, PSA 0.1–2.0 ng/mL, and no metastases on PSMA PET. Adverse events (AEs) were graded according to CTCAE v5.0. QoL was assessed using ICIQ-SF, IIEF 5, and EPIC-CP questionnaires at baseline and during follow-up. Minimal clinically important difference (MCID) was defined as >0.5 pooled standard deviations from baseline. Statistical analyses included ANOVA, logistic regression, and Cox models (p<0.05 significant).

Results:

Between April 2021 and September 2023, 100 patients (median age 71 years, range 52–84) were enrolled. Baseline characteristics and treatment details have been reported elsewhere. Median follow-up was 30.4 months. Late =G2 GU AEs occurred in 8.5%, including 1.1% G3 radiation cystitis. At multivariable analysis, higher baseline ICIQ-SF score (p=0.003, OR=1.32) and acute MCID worsening in ICIQ-SF (p=0.001, OR=20.5) independently predicted =G2 late GU AEs. One G2 late GI event was observed. EPIC QoL deterioration meeting MCID criteria was observed in 34% of patients (p=0.004), with 30% worsening in the EPIC urinary incontinence domain (p<0.001). On multivariable analysis, ICIQ-SF worsening was associated with shorter time from surgery (p=0.024), overall QoL deterioration with acute MCID (p=0.001), and EPIC urinary incontinence decline with higher bladder wall D25% (p=0.011).Median PSA at last follow-up was 0.03 ng/mL. Twenty-eight patients developed recurrence (median 14 months), with only three in-field relapses, indicating excellent local control. Biochemical recurrence-free survival rates were 90%, 83%, 77%, and 74% at 12, 18, 24, and 30 months, respectively. ISUP grade significantly predicted recurrence.

Conclusion:

Postoperative SBRT to the prostate bed results in a limited incidence of late grade =2 GU AEs, measurable changes in urinary PROs, and encouraging BRFS in patients with biochemical recurrence after prostatectomy. Longer follow-up and comparative studies are needed to better define its role in the salvage setting. (NCT04831970)