ESTRO 2025 - Abstract Book

S2093

Clinical - Urology

ESTRO 2025

4023

Poster Discussion Time to Undetectable PSA After Salvage Radiotherapy Predicts Biochemical Recurrence and Distant Metastasis in Post-Prostatectomy Patients Federico Mastroleo 1,2 , Giulia Marvaso 1,2 , Riccardo Villa 1,2 , Mattia Zaffaroni 1 , Maria Giulia Vincini 1 , Fabio Matrone 3 , Alessandro Magli 4 , Giulio Francolini 5 , Ciro Franzese 6,7 , Luca Nicosia 8 , Francesco Pasqualetti 9 , Luca Trodella 10 , Annamaria Vinciguerra 11 , Salvina Barra 12 , Giorgia Timon 12 , Matteo Augugliaro 13 , Corrado Spatola 14 , Vincenzo Burgio 15 , Maja Hasterok 16 , Marcin Miszczyk 16 , Marta Scorsetti 6,7 , Stefano Arcangeli 17 , Luca Triggiani 18 , Barbara Alicja Jereczek-Fossa 1,2 1 Division of Radiation Oncology, IEO European Institute of Oncology IRCCS, Milan, Italy. 2 Department of Oncology and Hemato-Oncology, University of Milan, Milan, Italy. 3 Radiation Oncology Department, Centro di Riferimento Oncologico (CRO), Aviano, Italy. 4 Department of Radiation Oncology, Udine University Hospital, Udine, Italy. 5 Radiation Oncology Unit, Azienda Ospedaliero Universitaria Careggi, Milan, Italy. 6 Department of Radiotherapy and Radiosurgery, IRCCS Humanitas Research Hospital, Rozzano, Italy. 7 Department of Biomedical Sciences, Humanitas University, Pieve Emanuele, Italy. 8 Radiation Oncology Department, IRCCS Sacro Cuore Don Calabria Hospital, Negrar di Valpolicella, Italy. 9 Radiation Oncology Unit, Azienda Ospedaliero Universitaria Pisana, Pisa, Italy. 10 Department of Radiation Oncology, Campus Bio-Medico University, Rome, Italy. 11 Radiation Oncology Unit, 12SS. Annunziata Hospital, “G. D’Annunzio” University of Chieti, Chieti, Italy. 12 Department of Radiation Oncology, IRCCS Ospedale Policlinico San Martino, Genova, Italy. 13 Radiation Oncology Unit, Azienda USL-IRCCS, Reggio Emilia, Italy. 14 Division of Radiation Oncology, Policlinico di Catania, Catania, Italy. 15 Division of Radiation Oncology, Azienda Ospedaliera SS Antonio e Biagio e Cesare Arrigo, Alessandria, Italy. 16 IIIrd Radiotherapy and Chemotherapy Department, Maria Sklodowska-Curie National Research Institute of Oncology Gliwice Branch, Gliwice, Poland. 17 Department of Radiation Oncology, San Gerardo Hospital, Monza, Italy. 18 Radiation Oncology Department, University and Spedali Civili Hospital, Brescia, Italy Purpose/Objective: Previous studies demonstrated that achieving an undetectable prostate-specific antigen (PSA) level (<0.1 ng/mL) following salvage radiotherapy (SRT) after radical prostatectomy (RP) predicts improved outcomes. This study aimed to stratify patients based on PSA response and time to PSA nadir after SRT, assessing their prognoses on biochemical relapse-free survival (BRFS) and distant metastasis-free survival (DMFS). Material/Methods: Data have been acquired from centers joining the AIRO-URO initiative to create a multi-institutional retrospective database including patients treated with SRT for BR after RP. Exclusion criteria were (1) pre-SRT PSA > 1.6 ng/mL; (2) receipt of ADT between RP and SRT or during SRT. Time to lowest post-SRT PSA (nadir) was calculated and patients were stratified into four groups: Group A achieved undetectable nadir-PSA after 6 months; Group B achieved undetectable nadir-PSA within 6 months; Group C did not achieve undetectable nadir-PSA and the nadir was reached within 6 months; Group D did not achieve undetectable nadir-PSA and nadir was reached after 6 months. Kaplan – Meier analysis and CoxPH-regression were used for the analysis of BRFS and DMFS. Results: A total of 1,091 patients were included (Table 1) with a median follow-up equal to 4.36 years [IQR, 2.61 – 6.32]. BR was experienced by 380 patients with a median time of 8.62 [95%CI: 6.93-NA] years, while DM was experienced by 118 patients, median time not reached. Group A included 617 patients with median nadir-PSA equal to 0.01 [IQR, 0.01-0.03] ng/ml reached within 15 [IQR, 9 25] months, meanwhile group B included 221 patients with median nadir-PSA equal to 0.02 [IQR, 0.01-0.06] reached within 3 [IQR, 3-5] months. Group C included 155 patients with median nadir-PSA equal to 0.41 [IQR, 0.20-0.81] ng/ml reached within 3 [IQR, 3-5] months and Group D included 98 patients with median nadir-PSA equal to 0.20 [IQR, 0.15-0.30] reached within 9 [IQR, 7-14] months. The five-year BRFS and DMFS rates are assessed in Figure 1, showing significant difference among the different groups (p < 0.001).