Intra-procedural CT control versus ultrasound only in ultrasound-guided thermal ablation of colorectal liver metastases: a single-centre cohort study

BACKGROUND: Local ablative treatment is increasingly used for small colorectal liver metastasis (CRLM). Adequate ablative margins are essential for achieving local control, yet reported rates of local tumour progression (LTP) vary widely. This study compared LTP rate after ultrasound (US)-guided ablation of CRLM performed with versus without intraoperative CT control. METHODS: All percutaneous US-guided ablations for CRLM performed in a single centre from 2018 to 2021 were reviewed for LTP. Procedures with intraprocedural CT (CT group), allowing immediate re-ablation for margin extension, were compared with procedures without intraprocedural CT control (OR group). RESULTS: A total of 152 procedures in 137 patients were analysed. In the CT group, 5 LTP events (8.0%) occurred after 62 procedures, affecting 5 of 111 CRLM (4.5%). In the OR group, 20 LTP events (22.2%) occurred after 90 procedures, affecting 22 of 132 CRLM (16.6%) (procedure-based and lesion-based p = 0.0035 and p = 0.0255), respectively. For CRLM ≤ 10 mm visualized with US, LTP occurred in 1/50 lesions (2%) in the CT group and 0/51 lesions (0%) in the OR group (p = 0.495). Most LTP occurred with synchronous recurrence elsewhere in the liver (CT group 3/5 [60%], OR group 16/22 [73%]). Only minor complications, Accordion grades 1-2, were observed with similar frequency (8% vs. 12% in CT group and OR group, respectively). CONCLUSION: Intraprocedural CT control was associated with substantially lower LTP, suggesting that CT control should be considered standard when available. US-only ablation may remain appropriate for small, clearly visualized lesions.