ESTRO 2023 - Abstract Book

S1111

Digital Posters

ESTRO 2023

Conclusion Differences were observed among centers in the management of EC and GEJC. The results of this survey provide baseline data for future research and to harmonize treatment recommendations for EC and GEJC patients in Italy.

PO-1382 Repeated Magnetic Resonance Image-guided Stereotactic body Radiotherapy for oligometastatic patients

G. Panza 1 , G. Chiloiro 1 , L. Boldrini 1 , A. Romano 1 , L. Placidi 2 , M. Nardini 2 , M. Galetto 3 , F. Cellini 1 , V. Valentini 1,4 , M.A. Gambacorta 1,3 1 Fondazione Policlinico Universitario Agostino Gemelli IRCCS, , Radioterapia Oncologica , ROMA, Italy; 2 Fondazione Policlinico Universitario Agostino Gemelli IRCCS, , Fisica Medica, ROMA, Italy; 3 Università Cattolica del Sacro Cuore, Facoltà di Medicina e Chirurgia, ROMA, Italy; 4 Università Cattolica del Sacro Cuore , Facoltà di Medicina e Chirurgia, ROMA, Italy Purpose or Objective Oligo-progression of irradiated metastatic site or further recurrence are becoming an open issue in the multi-integrated clinical management of oligometastatic disease (OMD). In this clinical scenario, re-irradiation with stereotactic technique, could represent the finest and repeatable treatment option for enhancing the course of OMD in term of local control and progression free survival. Moreover, the introduction of hybrid magnetic resonance imaging Stereotactic Body Radiotherapy (SBRT) allows real-time tumor tracking (cine-MRI) and to perform online adaptive radiotherapy (oART). Aim of this study is to retrospectively evaluate the efficacy and toxicity profile of Magnetic Resonance image-guided repeated SBRT (MRIg-reSBRT) in a OMD settings. Materials and Methods We retrospectively analyzed pts with in-field liver or perihepatic abdominal carcinosis recurrence candidate to MRIg reSBRT. Second SBRT doses were determined based on the tumor and distance to Organs at Risks (OaRs). Toxicities were assessed using the Common Terminology Criteria for Adverse Events (CTCAE) scale version 5. Overall response rate (ORR= partial and complete response) and clinical benefit (CB= ORR and stable disease) were assessed at 12 months from the end of reSBRT. Progression-free survival (PFS) and overall-survival (OS) at 12 months were calculated using the Kaplan Meier analysis. Results From July 2019 to January 2020 18 pts completed prescribed course of MRIg-reSBRT for 24 metastatic liver lesions, with a mean interval of 8,61 months (range 2-28) from the first SBRT. First stereotactic treatment was delivered on MR-Linac except for two patients. Table 1 summarize pts characteristic. At least an overlap of the 5% isodoses of prescription dose between the first and second SBRT were reported. For a few cases (22%) there were a minimal overlap between highest isodoses, at least 50% of prescription dose. Fig.1 The mean prescribed dose for the first treatment was 43 Gy (range 24-50Gy, mean BED α / β 10=93).