Introduction: Irreversible electroporation (IRE) is a non-thermal, tissue-ablation technique which brings about cellular destruction by means of a series of short high-voltage electric pulses. The absence of a thermal effect means that IRE can be effective in the ablation of tumours in the proximity of main blood vessels, nerve structures and, in the case of the liver, biliary conduits.
Objectives: To update the report entitled "Effectiveness and safety of irreversible electroporation for treatment of pancreatic and hepatic cancer. A systematic review ", published in 2014, which aimed to assess the effectiveness and safety of tumor resection by irreversible electroporation in the treatment of pancreatic cancer and primary and metastatic liver cancer, compared to other ablative techniques and the standard treatment.
Methods: A search stipulating no time limit was made of the scientific literature from December 2013 to December 2015, in the following databases: Medline; Embase; HTA, DARE, NHSEED; Reporter; Cochrane Database; IBECS; IME; ISI Web of Knowledge; Biomed Central; Clinical Trials Registry; CenterWatch; and Current Controlled Trials. Of the papers yielded, only those that met the selection criteria were selected. The data were then extracted using a purpose-designed form and summarised in evidence tables. The studies were classified according to their methodological quality using the Institute of Health Economics (IHE) scale for assessment of observational studies.
Results and discussion: Thirteen new studies, all of an observational nature, met the selection criteria and were added to the 9 studies already included in the previous report. Some studies had methodological limitations which could affect the results on effectiveness and safety, as well as potential conflicts of interest. In the treatment of pancreatic tumours, IRE achieved a higher survival rate -both overall and free of local and distal recurrence- than did the standard treatment (chemoradiotherapy). Other studies reported event-free survival of 6.7 months, and local-disease-free survival of 5.5 and 12.6 months (in patients with and without recurrence respectively). Specific adverse effects of pancreatic IRE were portal vein thrombosis (7.4%), ascites (5.6%), and biliary and pancreatic leaks (3.7%). In the only comparative study of liver tumors treated with IRE or radiofrequency no differences were observed in the post-procedural pain. In the remaining studies, wide variability was observed in the percentage of complete response, ranging from 18% to 100%. The most frequent complications were transient alanine aminotransferase elevations, pain, urinary retention, bile duct dilatation and cardiac arrhythmias.
Conclusions: The available scientific evidence on this technique's effectiveness and safety is based on a small number of observational studies, some with methodological limitations and possible biases that might affect the results. Heterogeneity when it comes to establishing and defining outcome variables, in patient populations and in the approach to IRE, renders inter-study comparison of results difficult. What this means is that no conclusions can be drawn as to whether IRE is more effective and safer than other ablation techniques or the standard treatment, until such a time as there are results yielded by studies having a good methodological design and a long-term follow-up.