ESTRO 2025 - Abstract Book

S2063

Clinical - Urology

ESTRO 2025

3641

Digital Poster Stereotactic body radiotherapy in prostate cancer: Results from a Chilean cohort

José Solís Campos 1,2 , Gabriel Lazcano Álvarez 1,2 , Darlett Folch Mora 1 , Tomás Walter Martin 1 , Francisco Pérez Peña 1 , Anaís Molina Cárcamo 3 , Florencia Olivares Duval 3 , Josefa Giusti-Bilz Schäfer 3 , Ilan Perrot Rosenberg 1,2 , Gabriel Veillon Contreras 1,2 , Benjamín Tudela Staub 1,2 , Ximena Quintela Dávila 1,2 1 Radiation Oncology, Universidad de Valparaíso, Valparaíso, Chile. 2 Oncology, Hospital Carlos Van Buren, Valparaíso, Chile. 3 School of Medicine, Universidad de Valparaíso, Valparaíso, Chile Purpose/Objective: Stereotactic body radiotherapy (SBRT) is an emerging alternative for the radical treatment of prostate cancer. The aim of this study is to describe efficacy and toxicity outcomes in a cohort of patients treated at Carlos Van Buren Hospital, which is part of the Chilean public health-care system. Material/Methods: Retrospective cohort of patients treated with curative intent between 2020 and 2024, with a prescription of 36.25 Gy in 5 fractions to the prostate, with ≥85% of the CTV receiving 40 Gy. Seminal vesicles irradiated according to risk. High-risk patients were not treated with pelvic radiotherapy. Planning was done using computed tomography and magnetic resonance imaging, without fiducials markers. VMAT technique was administered with a VersaHD linear accelerator (Elekta AB, Sweden) with 6MVFFF photons. Additionally, 6 months of androgen deprivation therapy was administered for intermediate-risk disease and 18-36 months for high-risk disease. Data were collected from clinical records and processed in STATA18 (StataCorp LLC, USA). Evaluation of biochemical control according to Phoenix criteria, and RTOG scale for grading gastrointestinal (GI) and genitourinary (GU) toxicities. The study was approved by the local ethics committee. Results: A total of 357 patients were included, with a median follow-up of 19.6 months (IQR 12,2 – 28.7), median age of 72 years (IQR 67-75), median of ECOG 0 (IQR 0-0), median of IPSS 8 (IQR 5-14), and median of PSA at diagnosis of 10.5 ng/mL (IQR 7.02-19.54). Risk distribution was: 15.77% low-risk disease, 39.88% intermediate risk, and 44.34% high risk. The biochemical control at 24 months in the low, intermediate and high risk group was 100%, 100% and 99% respectively (Figure 1). GU toxicity ≥3 at 6, 12, 18, 24, and 36 months was 2.1%, 1.3%, 0.9%, 0%, and 3.6%, respectively. At any analysis point 33.93% were asymptomatic, and 62.41% had G1- G2 toxicity, GU toxicity ≥3 was reported at 3.66% GI toxicity ≥3 at 6 and 12 months was 2.7% and 1.3%, with 0% at 18 -36 months. At any analysis point 59.52% were asymptomatic, and 37.21% had G1- G2 toxicity. GI toxicity ≥3 was reported at 3.27%.