ESTRO 2025 - Abstract Book

S1966

Clinical - Urology

ESTRO 2025

Patients with BR (PSA > 0.2 ng/ml) post-radical prostatectomy, confirmed to have macroscopic prostate bed recurrence via PSMA or Choline PET and further validated with Magnetic Resonance Imaging (MRI), were recruited. Treatment involved CyberKnife stereotactic SSRT targeting the macroscopic prostate bed relapse, delivering a total dose of 35 Gy in 5 fractions. Concomitant Androgen Deprivation Therapy (ADT) was prohibited. Complete Biochemical Response (CBR) and Biochemical response (BR) were defined as an absolute PSA nadir < 0.2 ng/ml and PSA reduction of > 50% from baseline at 3 months after treatment, respectively. Other outcomes of interest were biochemical, radiological and androgen deprivation therapy free survival (bPFS, rPFS and aPFS). Results: Up to date, 51 patients have been enrolled with a median follow up of 16 months (95%CI 16-22). CBR and BR were observed in 23 (45.1%) and 41 (80.4%) cases, respectively. bPFS, rPFS and aPFS events were detected in 12, 5 and 6 patients, respectively (median NR for all outcomes). Acute G2 GI and GU adverse events were reported in 2 cases each, while only 1 G2 late GI toxicity event was detected. No G>3 adverse events were recorded. Conclusion: Early results from STARR trial suggest promising outcomes after SSRT for patients with macroscopic prostate bed relapse and provide reassurance regarding the SSRT approach in this specific context. Biochemical outcomes are interesting especially considering the avoidance of any concomitant ADT within the trial. Only mild toxicity was reported, underlining the safety of the treatment. Moreover, SSRT may be considered a convenient approach considering the shorter treatment duration if compared to standard approach. References: [1]Francolini G,Jereczek-Fossa BA,Di Cataldo V,Simontacchi G,Marvaso G, Gandini S,Corso F,Ciccone LP,Zerella MA,Gentile P,Bianciardi F,Allegretta S,Detti B,Desideri I,D'Angelillo RM,Masi L,Ingrosso G,Di Staso M,Mazzeo E,Trippa F,Lohr F,Bruni A,Livi L.Stereotactic or conventional radiotherapy for macroscopic prostate bed recurrence:a propensity score analysis.Radiol Med.2022Apr;127(4):449-457.doi: 10.1007/s11547-022-01465-w.Epub 2022 Mar 5. [2]Francolini G.,Jereczek-Fossa B.A.,Di Cataldo V.,Simontacchi G., Marvaso G., Zerella M.A., Gentile P., Bianciardi F.,Allegretta S., Detti B., Masi L., lo Russo M. and Livi L. (2020), Stereotactic radiotherapy for prostate bed recurrence after prostatectomy, a multicentric series. BJU Int, 125: 417-425. Digital Poster Prospective evaluation on ultrahypofractionated online adaptive radiotherapy of prostate cancer on a 1.5 T MR-Linac: toxicity and oncologic outcomes Vlatko Potkrajcic 1 , Frank Paulsen 1 , David Baumann 1 , Evgeny Zharov 1 , Hathal Haddad 1 , Simon Böke 1 , Sarah Kübler 1 , Jessica Boldt 1 , David Mönnich 1 , Moritz Schneider 2 , Otilia Voigt 1 , Monica Lo Russo 1 , Benjamin Tengler 1 , Cihan Gani 1 , Daniela Thorwarth 1 , Maximilian Niyazi 1 , Elgin Hoffmann 1 1 Department of Radiation Oncology, University Hospital Tübingen, Tübingen, Germany. 2 Department of Radiation O, University Hospita, Tübingen, Germany Purpose/Objective: Published data on (ultra)hypofractionated radiotherapy (UHF-RT) in prostate cancer suggest equal oncologic outcomes and toxicity rates compared to normofractionated radiotherapy. Therefore, UHF-RT has gained increased attention and its use has been implemented in clinical routine. All patients with prostate cancer treated with UHF online adaptive MRI-guided RT on a 1.5 T MR-Linac within our department were evaluated regarding acute and late toxicity in this prospective study, using physician-recorded and patient-reported longitudinal toxicity. Keywords: prostate cancer, SBRT,PSA 1660