Irreversible Electroporation for Liver Metastases from Colorectal Cancer: A Systematic Review

Background: Irreversible electroporation (IRE) is a non-thermal form of ablation based on the delivery of pulsed electrical fields. It has been used to treat liver lesions, particularly those in proximity to major hepatic vasculature. The role of this technique in the portfolio of treatments for colorectal hepatic metastases has not been clearly defined. This study undertakes a systematic review of IRE for treatment of colorectal hepatic metastases. Methods: The study protocol was registered with the PROSPERO register of systematic reviews (CRD42022332866) and reports in compliance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA). The Ovid MEDLINE (R), EMBASE, Web of Science and Cochrane databases were queried in April 2022. The search terms 'irreversible electroporation', 'colon cancer', 'rectum cancer' and 'liver metastases' were used in combinations. Studies were included if they provided information on the use of IRE for patients with colorectal hepatic metastases and reported procedure and disease-specific outcomes. The searches returned 647 unique articles and the exclusions left a total of eight articles. These were assessed for bias using the methodological index for nonrandomized studies (MINORS criteria) and reported using the synthesis without meta-analysis guideline (SWiM). Results: One hundred eighty patients underwent treatment for liver metastases from colorectal cancer. The median transverse diameter of tumours treated by IRE was <3 cm. Ninety-four (52%) tumours were adjacent to major hepatic inflow/outflow structures or the vena cava. IRE was undertaken under general anaesthesia with cardiac cycle synchronisation and with the use of either CT or ultrasound for lesion localisation. Probe spacing was less than 3.2 cm for all ablations. There were two (1.1%) procedure-related deaths in 180 patients. There was one (0.5%) post-operative haemorrhage requiring laparotomy, one (0.5%) bile leak, five (2.8%) post-procedure biliary strictures and a zero incidence of post-IRE liver failure. Conclusions: This systematic review shows that IRE for colorectal liver metastases can be accomplished with low procedure-related morbidity and mortality. Further prospective study is required to assess the role of IRE in the portfolio of treatments for patients with liver metastases from colorectal cancer.