ESTRO 2023 - Abstract Book

S457

Sunday 14 May 2023

ESTRO 2023

Conclusion These updated data about efficacy and late toxicity confirm our previously published findings that the UHRT schedule with a concomitant boost on the DIL is a safe and effective approach. The increasing dose to the DIL does not worsen the RT toxicity and consequently does not affect patients' QoL, thus opening the possibility of an, even more, escalated treatment. PD-0576 Stereotactic reirradiation for locally recurrent prostate cancer after definitive radiotherapy G. Francolini 1 , C. Cerbai 2 , M.G. Carnevale 2 , V. Di Cataldo 1 , B. Detti 1 , M. Loi 1 , G. Frosini 1 , B. Guerrieri 2 , I. Morelli 2 , M. Roghi 2 , M. Ganovelli 2 , A. Allegra 2 , V. Salvestrini 3 , L. Visani 3 , E. Olmetto 1 , D. Greto 1 , G. Simontacchi 1 , M. Mangoni 2 , I. Desideri 2 , I. Meattini 2 , L. Livi 2 1 University of Florence, Radiation Oncology Unit, Azienda Ospedaliero Universitaria Careggi, Florence, Italy; 2 University of Florence, Department of Experimental and Clinical Biomedical Sciences "M. Serio", Florence, Italy; 3 Istituto Fiorentino di Cura e Assistenza (IFCA), Cyberknife Center, Florence, Italy Purpose or Objective Treatment of locally recurrent prostate cancer (pCa) after definitive radiotherapy (RT) is a matter of debate. Treatment alternatives in this scenario (e.g Salvage Prostatectomy or palliative androgen deprivation therapy, ADT) are burdened by a significant risk of toxicity. Stereotactic re-irradiation (re-SBRT) is an emerging approach potentially allowing a non- invasive local therapy. However, data confirming efficacy and tolerability are currently needed to support this technique in current clinical practice. Here we present a mono-centric cohort reporting long term clinical outcomes and safety after Cyberknife robotic re-SBRT for local recurrence after primary RT. Materials and Methods Data about 57 patients consecutively treated from June 2012 to February 2021 were collected and analyzed. All patients underwent previous definitive radiotherapy for non-metastatic pCa and were affected by biochemical relapse defined according to European Urology Association criteria. Macroscopic evidence of intra-prostatic recurrence was detected in all patients through 18F-choline PET/CT and Magnetic Resonance Imaging. Patients with metastatic or regional nodal disease were excluded. All patients underwent CyberKnife robotic reSBRT for a total dose of 30 Gy in 5 fractions every other day. During follow up, PSA was assessed at every 3 months following re-irradiation. Gastrointestinal (GI) and Genitourinary (GU) Toxicity was assessed at each scheduled visit by the Common Terminology Criteria for Adverse Events toxicity scale (CTCAE v.4.03). Results After a median follow up of 58.8 months (IQR 48.9-79), Biochemical Relapse (BR) was detected in 27 (47%) patients, for a median Median BR-free survival (BRFS) of 52.8 months (95% C.I. 36.4- 58.3). Metastases occurred in 15 pts (26%), median metastasis free survival (MFS) was not reached. 15 (26%) patients died, for a median OS of 83.2 months (95% C.I 79.3-83.2). At univariate analysis, PSA >2.5 ng/ml was significantly associated to worse BRFS (51.2 vs 30 months, p=0.03) and MFS (55.2 vs 41.3 months, p=0.04). Concurrent ADT was associated with worse MFS (55 vs 35.6 months, p=0.04). However, none of these factors persisted as an independent predictor of outcome at Cox multivariate analysis. G1, G2 and G3 late GI toxicity were recorded in 3, 2 and 1 pts respectively, while 11 and 8 patients developed G1 and G2 late GU toxicity. No late G3 GU adverse events were recorded. Conclusion Re-SBRT confirmed to be a safe and viable treatment option for local recurrence after definitive radiotherapy with 5 years of median follow-up. Prospective data are awaited to develop correct selection criteria and guide current clinical practice. PD-0577 Final analysis of the benchmark case RTQA procedure for the EORTC 1420 ‘Best of’ trial (NCT02984410) D. Portik 1 , E. Clementel 1 , C. Corning 1 , R.O. Olaniran 2 , J. Kazmierska 3 , E.M. Ozsahin 4 , W. Grant 5 , M. Tomsej 6 , L. Vieillevigne 7 , C. Simon 8 , V. Gregoire 9 , N. Reynaert 10 , N. Andratschke 11 1 European Organisation for Research and Treatment of Cancer (EORTC) Headquarters, RTQA, Brussels, Belgium; 2 European Organisation for Research and Treatment of Cancer (EORTC) Headquarters, Statistics, Brussels, Belgium; 3 Greater Poland Cancer Center, Radiotherapy, Poznan, Poland; 4 Centre Hospitalier Universitaire Vaudois (CHUV), Radiation Oncology, Lausanne, Switzerland; 5 Gloucestershire Hospitals NHS Foundation Trust, Radiotherapy, Gloucester, United Kingdom; 6 Centre de Radiothérapie du Hainaut, Radiotherapy, Charleroi, Belgium; 7 Institut Claudius Regaud (ICR), Institut Universitaire du Cancer de Toulouse-Oncopole (IUCT-O), Medical Physics, Toulouse, France; 8 Centre Hospitalier Poster Discussion: QA and auditing