S985
Clinical - Oligometastatic cancer
ESTRO 2026
imbalanced, there appears to be a dose-dependent interaction with IG-type. The impact of image guidance on LC was mostly seen in patients receiving lower doses, although further analyses are needed to determine whether there is a dose beyond which MR- guidance is no longer associated with improved LC. References: [1] de Mol van Otterloo SR, Christodouleas JP, Blezer ELA, et al. (2020) The MOMENTUM Study: An International Registry for the Evidence-Based Introduction of MR-Guided Adaptive Therapy. Front Oncol. 10:1328.[2] Kroese SGC, Pavic M, Stellamans K, et al. (2023) Metastases-directed stereotactic body radiotherapy in combination with targeted therapy or immunotherapy: systematic review and consensus recommendations by the EORTC-ESTRO OligoCare consortium. Lancet Oncol. 24:e121-e132 Keywords: Liver metastases, SBRT, image guidance Digital Poster 4029 Local control after SBRT for liver lesions: helical vs robotic IMRT. Gaia Parma 1 , Andrei Fodor 1 , Chiara Lucrezia Deantoni 1 , Miriam Torrisi 1 , Laura Giannini 1 , Sara Saufi 2 , Paolo Passoni 1 , Sara Broggi 3 , Claudio Fiorino 3 , Antonella Del Vecchio 3 , Stefano Arcangeli 2 , Nadia Gisella Di Muzio 1 1 Radiation Oncology, IRCCS San Raffaele Scientific Institute, Milan, Italy. 2 Radiation Oncology, IRCCS San Gerardo dei Tintori, Monza, Italy. 3 Medical Physics, IRCCS San Raffaele Scientific Institute, Milan, Italy Purpose/Objective: The purpose of this study is to compare the results obtained using two modern techniques of stereotactic body radiotherapy (SBRT) in the treatment of liver lesions at our institution. Material/Methods: From November 2005 to August 2025 132 liver lesions were treated with SBRT in 100 patients: 44 lesions with robotic delivery (CK) and 88 lesions with helical IMRT (TT). Primary tumors were mainly digestive (colon and pancreas cancer), breast, lung and gynecologic. The median gross tumor volume (GTV) were similar: 12.2 cc (0.20-109.73 cc) for CK vs 12.4 cc (0.30-418 cc) for TT; while PTV was smaller in the CK group for the narrower margins used. The median biologically equivalent dose (BED) prescribed was 85.5 Gy (45 Gy in 5 fractions) in both groups. A BED>100Gy was prescribed in 47.72% of the CK treatments vs 37.5% of TT treatments. Results: Twelve-months local relapse-free survival (LRFS) was 88.3% in the CK group vs 74.7% in the TT group, 24- months LRFS was 88.3% vs 64.5%, and 36-months LRFS was 79.4% vs 61.2%, with a difference between
patients receiving BEDD98>105Gy (Figure). With addition of this interaction, a significant association with LC was retained for BEDD98 (HR=0.99, p=0.023), MRI (HR=0.16, p=0.024) and CTV (HR=1.05/10 cm3, p=0.044).Treatment related adverse events grade ≥ 3 were observed in 2.5% of 402 patients.
Conclusion: Image-guided radiotherapy as locally ablative treatment for patients with liver oligometastases offers excellent LC . Although the databases are
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