ESTRO 2025 - Abstract Book

S1748

Clinical – Upper GI

ESTRO 2025

Purpose/Objective: Stereotactic Body Radiation Therapy (SBRT) is a safe and effective treatment for liver metastases or hepatocellular carcinoma (HCC) with a dose-response relationship for local control (LC). Proximity to organs at risk (OAR) often requires dose de-escalation. This study evaluated LC and recurrence patterns in patients administered hepatic SBRT in more than 4 fractions due to dosimetric constraints. Material/Methods: This retrospective study included 33 patients treated with SBRT (Cyberknife®) in more than 4 fractions for HCC or liver metastases, between January 2011 and December 2019. Patients were ineligible for treatment in 3 or 4 fractions due to OAR proximity. Recurrence patterns were analysed according to the volume shared between recurrence and initial target or treatment isodose volumes.

Results: The primary dose ranged from 35-50 Gy delivered in 5 to 7 fractions for the treatment of HCC (39%) or liver metastases (61%) mainly secondary to colorectal cancer (40%). LC rate was 64%, with 12 patients showing recurrence volume overlap with the initial target volume or treatment isodose. In-field recurrence occurred in only 12.5% of patients with most relapses being out-of-field. No grade ≥3 events were reported. Conclusion: Despite dose reductions to spare OAR, SBRT showed satisfactory LC with low toxicity. Out-of-field recurrence remains the most common pattern identified and likely related to underlying disease. Prospective data are necessary to determine whether preserving dose while reducing planning target volume (PTV) coverage could enhance LC. References: Robbins JR, SBRT for hepatocellular carcinoma: Practice patterns, dose selection and factors impacting survival. Cancer Med. 31 janv 2019 ; Kok END, High versus low dose SBRT for hepatic metastases. Clin Transl Radiat Oncol. janv 2020 ; Van Oirschot M, Determining Planning Priorities for SABR for Oligometastatic Disease: A Secondary Analysis of the SABR-COMET Phase II Randomized Trial. Int J Radiat Oncol. déc 2022 ; Joo JH, Local Control Outcomes Using SBRT for Liver Metastases From Colorectal Cancer. Int J Radiat Oncol. nov 2017 ; Eufemon Cereno R, Should OARs be prioritized over target volume coverage in SABR for oligometastases? a secondary analysis of the population-based phase II SABR-5 trial. Radiother Oncol. mai 2023 Keywords: SBRT, liver, local control