ESTRO 2025 - Abstract Book

S1151

Clinical – Lower GI

ESTRO 2025

259

Digital Poster Repeat SABR likely required for survival benefit in oligometastatic colorectal cancer: results from the prospective randomised SABR-SCAN trial Joachim Widder 1,2,3 , Rozemarijn Vliegenthart 4 , Caroline Van De Wauwer 5 , Harry JM Groen 6 , Johannes A Langendijk 3 , Jan F Ubbels 3 1 Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria. 2 Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria. 3 Department of Radiation Oncology, University Medical Center Groningen, Groningen, Netherlands. 4 Department of Radiology, University Medical Center Groningen, Groningen, Netherlands. 5 Dept of Cardiothoracic Surgery, University Medical Center Groningen, Groningen, Netherlands. 6 Dept of Pulmonary Diseases, University Medical Center Groningen, Groningen, Netherlands Purpose/Objective: The value of SABR for lung oligometastases (LOM) from colorectal cancer (CRC) is unknown. The SABR-SCAN trial (NCT02414334) investigated the effect of immediate versus delayed SABR on PFS in these patients. Material/Methods: Patients with up to three LOM from CRC were included. Primary tumours had to be resected, there should be no evidence of extrapulmonary metastases, and any previous metastases were to be resected or ablated. No prior palliative chemotherapy was permitted. Consenting patients were randomised to immediate SABR of LOM (standard) versus follow-up with CT at three-monthly intervals and SABR of LOM upon lesion progression (experimental arm). Any progression was discussed at the multidisciplinary tumour board and further local treatment of metastases was recommended if all lesions were amenable to SABR, thermal ablation, or resection. Systemic therapy was recommended at polymetastatic progression only. The primary endpoint was PFS at one year. Secondary endpoints were OS and time-to-failure-of-local-strategy (date of randomisation to polymetastatic progression unamenable to metastasis directed therapy (MDT), or death). Quality of life (QoL) was assessed two years from randomisation using EuroQol-5D, EORTC-LC13, and HADS. Results: Twelve patients were randomised between 1/2016 and 4/2017 before the study was closed early due to slow accrual. Median age was 69y (50-70; 8 males). Median follow-up for surviving patients was 80 months (min63 max85). In the immediate-SABR-arm, four out of the seven patients (57%) had oligoprogression (new lesions) within the first year and underwent re-MDT. In the delayed treatment arm, all index lesions had progressed at the three month CT scan and were treated. PFS at 1 year (primary endpoint) was therefore 43% (95%CI, 18%-100%) vs 0% (HR=18, 95%CI, 2-165, p=0.0017).