ESTRO 2025 - Abstract Book

S1995

Clinical - Urology

ESTRO 2025

toxicity reduction compared to historical series, assessed via CTCAE v5.0. Secondary end-points include genitourinary (GU) toxicity, quality of life (EORTC QLQ-C30, EPIC), and biochemical failure.

Results: The results of the first 840 treatment fractions in 42 patients are reported. Median age was 64 years (range 33-78). Median PSA before RT was 0.43 ng/ml (0.1-3.12 ng/ml). Gleason score was: 6 (7%), 7 (59.5%), 8-9 (33.5%). Initial stage was pT2 (54.8%), pT3 (45.2%), pN0 (76.2%), pN1 (2.4%), and pNx (21.4%). Sixteen (37.2%) had biochemical relapse only, while 27 (62.8%) had macroscopic relapse. The pelvis was treated in 17 (39.5%) cases. End of treatment acute proctitis was: G1 20.9%, G2 2.3%; acute diarrhea was: G1 14%, G2 7%; acute cystitis was: G1 16.3%, G2 2.3%. In the univariate analysis, the only factor associated with diarrhea onset was the inclusion of the pelvis (G1: 29.4% versus 3.8%, G2: 17.6% versus 0%; p=0.002). There was no difference in acute toxicity between treatment dose (p=0.62). Conclusion: Preliminary data seems to show minimal acute toxicity. CT-based adaptive moderate hypofractionated radiotherapy might be beneficial in the PC postoperative setting. A longer follow up is needed to confirm these data and evaluate late toxicity.

Keywords: Prostate cancer, salvage RT, adaptive radiotherapy

2344

Digital Poster Long-term outcomes and treatment efficacy in high-risk prostate cancer patients treated with stereotactic extreme hypofractionated radiotherapy Vivien Molnár 1 , Gábor Stelczer 1 , Gábor Kontra 1 , István Nahaji 1 , Zsuzsa S. Kocsis 2,3 , Levente Varga 1 , László Gesztesi 1 , Kliton Jorgo 1,4 , Zoltán Takácsi-Nagy 1,3,4 , Csaba Polgár 1,3,4 , Péter Ágoston 1,4 1 Centre of Radiotherapy, National Institute of Oncology, Budapest, Hungary. 2 Department of Radiobiology and Diagnostic Onco-Cytogenetics, Centre of Radiotherapy, National Institute of Oncology, Budapest, Hungary. 3 National Tumor Biology Laboratory, National Institute of Oncology, Budapest, Hungary. 4 Department of Oncology, Faculty of Medicine, Semmelweis University, Budapest, Hungary Purpose/Objective: According to our in house protocol pelvic irradiation can be omitted in patients with non-metastatic high risk (HR) prostate cancer over 70 years of age or with severe comorbidities. To determine the outcome and toxicity of local prostate stereotactic radiotherapy without lymph node irradiation using the CyberKnife (CK) device for elderly patients or for patients with comorbidities. Material/Methods: Our retrospective analysis included 262 patients with non-metastatic (clinically N0M0) high-risk (HR) (either Gleason score ≥8 or PSA ≥20, or clinical stage ≥T2c) and very high -risk (VHR) (at least two criteria of the mentioned) prostate cancer who were treated according to a prospective protocol between May 2018 and February 2022. Patients received 5x6-6,5 Gy to the seminal vesicles and 5x7-8 Gy to the prostate with stereotactic CK treatment using a simultaneous integrated boost technique. Endpoints were: Biochemical and clinical relapse-free survival (BRFS, CRFS), disease-free (RFS), disease-specific (DSS) and overall survival (OS). Treatment outcomes were analyzed based on hormonal treatment (HT) duration – comparing short (< 6 months) and long HT (≥12 months) groups. Early and late urogenital (UG) and gastrointestinal (GI) side effects caused by radiation and their association with HT were also investigated. Data analysis was performed using the Log-Rank test, the Mann-Whitney U test and Kaplan-Meier analysis with a significance level set at 0.05.