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.