Nonthermal Ablation Safe, Feasible for Liver Cancer

A novel ablation technique that does not rely on heat or cold is a safe and feasible way to target malignant liver lesions that are difficult to ablate because of their proximity to major arteries and veins, according to new research.
"Other ablation techniques, including radiofrequency ablation, use either heat or cold to destroy malignant lesions," Philippe Wiggermann, MD, from the University of Regensburg in Germany, told Medscape Medical News.
"If you use conventional ablation, you have this 'heat sink' effect and you risk destroying larger vessels if the lesions are close to an artery or portal vein. However, with percutaneous irreversible electroporation, strong electrical pulses cause permanent disruption of the cell membrane, and the ablated tissue dies without causing collateral damage," Dr. Wiggermann explained.
His team used percutaneous irreversible electroporation to treat 28 liver tumors not suitable for conventional therapy or located in an area not amenable for radiofrequency ablation.
Dr. Wiggermann presented the results at the American Roentgen Ray Society 2013 Annual Meeting in Washington, DC.
"Patients must be treated under general anesthesia and given neuromuscular blockade," Dr. Wiggermann pointed out. "Otherwise, the strength of the electrical impulse (3000 volts) would cause all of the muscles in the body to contract at the same time."
Electrocardiographic gating is essential to synchronize the delivery of the electric impulses with contractions of the heart. As is the case with other ablation procedures, electrodes are placed percutaneously in the target liver lesion using computed tomography (CT) and ultrasound guidance.

We can redo these lesions as many times as we want, so as soon as we realize any viable tumor remains, we can repeat the procedure.

Of the 28 malignant liver lesions treated by the team so far, complete ablation of viable tumor tissue was achieved in 21 tumors. Complete ablation was documented with contrast-enhanced ultrasound, CT, and magnetic resonance imaging 24 hours after the intervention.
"We can redo these lesions as many times as we want, so as soon as we realize any viable tumor remains, we can repeat the procedure," Dr. Wiggermann said.
In their small series to date, there have been 4 adverse events: 1 minor pneumothorax, 2 partial thromboses of the left portal vein, and 1 postanesthetic upper plexus palsy.
"We've also treated lesions in the prostate and the kidney, as well as large sarcomas with palliative intent," Dr. Wiggermann noted. "So this technique broadens the spectrum of where you can do ablation safely for local tumor treatment. From the patients' perspective, it's really a minimally invasive approach."
Irreversible electroporation represents an early novel therapy for the treatment of unresectable liver tumors that are in close proximity (1 cm or less) to vital vascular and biliary structures, said Robert Martin II, MD, from the University of Louisville in Kentucky, who was asked by Medscape Medical News to comment on the study.
"In the appropriate technical hands, it is both a safe and an effective therapy for lesions 3 cm or less in size, with excellent completion ablation results," Dr. Martin said. However, he cautioned that continued quality assurance is necessary to make sure that the procedure achieves an ablation efficacy rate in excess of 95% and a recurrent need for ablation of less than 7% to ensure that its use remains both appropriate and effective.

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