Irreversible electroporation of a liver metastasis

Abstract

A 70 year old Caucasian man with a history of recently resected moderately-differentiated invasive adenocarcinoma of the colon presented with a 1.8 cm focal liver lesion in segment V (white arrow in Figs. a and b) newly diagnosed at MRI. No other metastatic lesions were detected at PET-CT. After discussing treatment options including resection and ablation, a decision was made to proceed with ablation of this single metastasis. An MRI performed the day after the procedure demonstrates a large area of ablation at the site of the metastasis before contrast administration (white arrow in Fig. c). The ablated area demonstrated no contrast enhancement and was surrounded by an enhancing rim after contrast medium administration (white arrow in Figs. d and e), this findings are consistent with successful metastatic lesion ablation. In Figs. 1d and 1e (black arrow), a contrast-filled vessel is clearly identified crossing the area of ablation. The vessel is not seen before contrast medium administration (black arrow in Fig. c). Irreversible electroporation causes an area of necrosis/apoptosis demonstrating no enhancement on post-contrast images (Figs. d and e) (1–3). While peripheral enhancement surrounding a zone of necrosis has been reported following chemoembolization, the significance of the post-IRE MRI changes has not been adequately studied (Figs. 1d and 1e), in this case the peripheral enhancing area demonstrates high signal intensity on diffusion weighted images (Fig. 1f) (1–3). Thirty days later, in the area of ablation, there has been complete radiological liver parenchyma regeneration (Fig. g), and only a mild perfusion abnormality is noted, the vessel spared by IRE is still patent. Metastatic colorectal carcinoma to the liver is common and treatment of single focal metastatic lesions may be achieved with multiple techniques such as surgical resection, radiofrequency ablation, cryoablation, highly focused ultrasound, microwave ablation and irreversible electroporation (IRE) (1). Each of these techniques has its specifics indications, benefits and risks. Stemming from its non-thermal nature, irreversible electroporation has the peculiar characteristic of ablating cells while sparing structural elements of the biliary ducts and vessels (1, 2). IRE consists of targeted delivery of electrical pulses to modify cell membrane permeability, either temporarily or permanently, depending on the electric field magnitude, pulse duration, and number of pulses applied (1, 2). IRE causes tissue necrosis and apoptosis through the formation of nanometer-scale pores in the cell membrane (1, 2). MRI characteristics of treated lesions have been described in rats (2), but the experience in humans is still limited. These images represent early changes following IRE with demonstration of vessel sparring by IRE.