ESTRO 2025 - Abstract Book

S2132

Clinical - Urology

ESTRO 2025

Keywords: Prostate, Focal Dose Escalation, Clinical Trial

4391

Digital Poster Prognostic Significance of 6-Months Undetectable Post-Treatment PSA Levels in Prostate Cancer Patients Undergoing Radiotherapy Combined with ADT Federico Mastroleo 1,2 , Giulia Marvaso 1,2 , Chiara Lorubbio 1,2 , Ilaria Repetti 1,2 , Maria Giulia Vincini 1 , Mattia Zaffaroni 1 , Cristiana Fodor 1 , Giovanni Carlo Mazzola 1 , Dario Zerini 1 , Barbara Alicja Jerczek-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 Purpose/Objective: Current literature showed the prognostic role of prostate-specific antigen (PSA) at 6 months after radiotherapy (RT) in localized prostate cancer (PCa). In this setting, this study aimed to evaluate the prognostic significance of undetectable (< 0.1 ng/ml) six months PSA following curative RT + androgen-deprivation therapy (ADT) in PCa patients. Material/Methods: We retrospectively included patients (1) with histologically confirmed PCa; (2) treated with curative RT+ADT for unfavorable-intermediate, high-risk and very high-risk PCa; (3) with a follow up of at least one yars. At the end of RT treatment PSA measurements were performed every 3 months. Biochemical recurrence (BR) was assessed according to Phoenix definition while clinical recurrence (CR) was defined as the presence of local, regional or distant metastasis (DM) at radiological imaging. The PSA level recorded at six months after RT completion was analyzed and categorized as either undectable (<0.1 ng/mL) or detectable (≥0.1 ng/ml) and included as variable in the analysis. Biochemical regression-free survival (BRFS), Clinical Progression Free Survival (CRFS) and Distant Metastasis Free Survival (DMFS) were assessed by Kaplan-Meier survival analysis and CoxPH-regression. All patients signed an informed consent for research purposes and the study received institutional review board approval. Results: A total of 241 patients were included with a median follow-up was 2.49 years (IQR: 1.53 – 4.16). Patient and treatment characteristics are detailed in Table 1. An undetectable PSA level (< 0.1 ng/mL) at six months was achieved in 76 patients (32%). Thirty-three patients experienced BR. The 3-year BRFS rate was 96.3% in patients with undetectable PSA compared to 84.4% in those with detectable PSA (p=0.009) (Fig.1a). Multivariate Cox regression analysis identified ISUP 4-5 (HR:3.08; 95%CI:1.48 – 6.41; p=0.003) and 6-months undetectable PSA (HR:0.26; 95%CI:0.09 – 0.83; p=0.011) as BRFS independent predictors. CR was experienced by 22 patients. The 3-year CRFS rate was 98.4% in patients with undetectable PSA compared to 85.8% in those with detectable PSA (p=0.005) (Fig.1b). ISUP 4-5 [HR:3.66; 95%CI:1.52-8.83; p=0.004] and 6-months undetectable PSA [HR:0.09; 95%CI:0.01-0.66; p=0.018] were independently predictors of CRFS. DM was experienced by 11 patients. The only independent predictor for DMFS was ISUP 4-5 (HR:3.61; 95%CI:1.04 12.54; p=0.043), while 6-months undetectable PSA showed no significance.