Having performed over 400 irreversible electroporation (IRE) treatments at the University of Miami, Miami, USA, we believe that certain niche applications of the technology have demonstrated tremendous value and hold a lot of promise for our patients, writes Govindarajan Narayanan.
IRE uses high voltage, low energy DC current to induce cell death. It is commercially available as Nanoknife (Angiodynamics) and has a 510k approval from the USFDA for ablation in soft-tissue. Use of this technology in organs is considered off-label.
The first human IRE experience was published by Ken Thompson from The Alfred Hospital in Melbourne Australia.1 Since then, several publications both in the interventional radiology and surgical literature have studied the role of IRE in the liver, kidney, and pancreas. Being a predominantly non-thermal energy source, IRE is an appealing alternative in the world of percutaneous ablation and has enabled us at the University of Miami to use this technology in areas that are not amenable to percutaneous thermal ablation.
Having performed more than 400 IRE treatments at the University of Miami, we believe that certain niche applications of IRE have demonstrated tremendous value and hold a lot of promise for our patients. One of these key areas is in pancreatic ablation. Pancreatic cancer has a dismal prognosis with 50% of the patients having distant metastasis at the time of diagnosis. The majority of the pancreatic cancer patients are treated with chemotherapy lines or a combination of chemotherapy and radiation, with a very small percentage making it to surgery. Thermal ablative options have been tried in management of pancreatic cancer, mostly in the surgical setting with a high complication rate and without major success.
IRE in the pancreas was initially studied in a swine model by Charpentier et al and was concluded to be a safe method for pancreatic tissue ablation.2 The first percutaneous pancreatic IRE ablation at our institution was performed in November 2010 on a patient with stage three locally advanced pancreatic cancer. The patient was successfully downstaged to surgery in 2011, and is alive to date. Our multidisciplinary group published the data on the first human series using IRE percutaneously, to treat pancreatic cancer in 14 patients.3 This demonstrated the safety, efficacy and the feasibility of using IRE in the pancreas in a minimally invasive fashion. Since then, the percutaneous technique has been reproduced and treatment performed at several centres worldwide.
Figure 1: CT scans showing pancreatic tumour with vascular encasement (A) treated with IRE (B). Post-treatment scans three months later (C and D). Subsequent surgical exploration yielded a margin-negative resection.
We also presented additional data on percutaneous IRE in the pancreas at ASCO 2014 showing an overall survival of 14.5 months for the entire cohort of stage three and four patients. Separating the data based on stage, LAPC patients had an overall survival of 16.2 months vs. 8.6 months for stage four patients. A majority of the lesions that were treated, involved the head of the pancreas, a location that is complex even from an open surgical standpoint. The average length of stay of most patients who undergo percutaneous pancreatic IRE, is around two days. While the early data are exciting and promising, we need more studies and randomised controlled trials to establish IRE in the treatment algorithm of pancreatic cancer.
The “heat-sink” effect impacts the ability to perform thermal ablations percutaneously when tumours are in close proximity to vasculature. In these instances, incomplete ablations and the possibility of vessel injury are real concerns. A retrospective review of data on 129 lesions in 101 patients has shown the advantage of IRE being used safely to treat tumours that are in close proximity to blood vessels or encasing them.4
Ablations near critical structures using thermal ablative techniques require dissection and pneumo-dissection. These add additional steps to the procedure and may not always yield the expected result. Canon et al demonstrated the safety of IRE in liver lesions close to vital structures5 and at University of Miami, we have used IRE safely in several patients with periaortic metastatic nodes and in locations that are in close proximity to critical structures such as gall bladder, bowel and bladder without any additional separation manoeuvres with durable results.
As a practice that uses all ablative modalities, we find that IRE serves as a valuable complement to the thermal ablative techniques. It has enhanced our capabilities as interventional oncologists to treat lesions in complex locations where thermal ablations and sometimes even trans-arterial treatments might not be viable. With results of prospective trials and retrospective studies that are underway, these “niche-applications” of today could very well be “mainstream applications” of tomorrow.‰Û¬
Govindarajan Narayanan is professor of Clinical Radiology and chief of Vascular and Interventional Radiology, University of Miami-Miller School of Medicine, Miami, USA. He is a consultant for Angiodynamics
References
1 Thomson KR, Cheung W, Ellis SJ, Federman D, Kavnoudias H, Loader-Oliver D, Roberts S, Evans P, Ball C, Haydon A: Investigation of the safety of irreversible electroporation in humans. Journal of Vascular and Interventional Radiology, 2011
2 Kevin P Charpentier,Farrah Wolf, Lelia Noble, Brody Winn, Murray Resnick, Damian E Dupuy : Irreversible electroporation of the pancreas in swine: a pilot study. HPB (Oxford). 2010;
3 Narayanan G, Hosein PJ, Arora G, Barbery KJ, Froud T, Livingstone AS, Franceschi D, Rocha Lima CM, Yrizarry J: Percutaneous irreversible electroporation for downstaging and control of unresectable pancreatic adenocarcinoma. Journal of Vascular and Interventional Radiology 2012
4 Narayanan G, Bhatia S, Echenique A, Suthar R, Barbery K, Yrizarry J. Vessel patency post irreversible electroporation. Cardiovascular Interventional Radiology. 2014
5 Cannon R, Ellis S, Hayes D, Narayanan G, Martin RCG: Safety and early efficacy of irreversible electroporation for hepatic tumors in proximity to vital structures. Journal of Surgical Oncology 107:544–549, 2013
