Irreversible Electroporation for Colorectal Liver Metastases: Long-term Outcomes from a Transatlantic Multicenter Study.

PURPOSE: To evaluate safety and long-term oncologic outcomes of irreversible electroporation (IRE) for colorectal liver metastases (CRLM) across three high-volume expert centres. MATERIALS AND METHODS: This retrospective multicentre study included patients treated with IRE for unresectable and unablatable CRLM between 2012 and 2025. The primary outcome measure was local tumour progression free-survival (LTPFS). Secondary outcome measures included local control (LC) allowing repeat treatment, overall survival (OS), distant progression-free survival (DPFS), adverse events (AE; CTCAE v5.0) and length-of-hospital-stay. RESULTS: Overall, 162 patients underwent 191 IRE procedures for 219 tumours. Median follow-up was 33.7 months. Per-tumour LTPFS at 1, 2, and 3-years was 68.2%, 55.5%, and 52.6%. Tumours ≤ 3cm demonstrated superior LTPFS compared with tumours >3cm, with 1, 2 and 3-year LTPFS rates of 77.5%, 63.8%, and 60.3% versus 37.4%, 28.5, and 28.5%, (HR 2.89; 95% CI 1.82-4.60; p<0.001). LTPFS did not differ between centres (p = 0.80). Per-tumour LC rates at 1, 2, and 3-years were 97.4%, 95.7%, and 94.8%. OS at 1, 3, 5 and 10-years was 89.3%, 44.6%, 24.2%, and 14.0%. AEs occurred in 23.0% of procedures, predominantly grade 1-2 (72.7%); no grade 5 events occurred. Median hospital-stay was 1 day (IQR 1-2). CONCLUSION: IRE is a feasible and safe treatment option in expert centres for selected patients with CRLM, ineligible for thermal ablation or resection. Tumour size is a key determinant of LTP, with superior outcomes in lesions ≤ 3cm. Local recurrences are frequently amenable to repeat local treatment, eventually resulting in durable LC in the majority of patients.