Tumor ablation with irreversible electroporation

Abstract

We report the first successful use of irreversible electroporation for the minimally invasive treatment of aggressive cutaneous tumors implanted in mice. Irreversible electroporation is a newly developed non-thermal tissue ablation technique in which certain short duration electrical fields are used to permanently permeabilize the cell membrane, presumably through the formation of nanoscale defects in the cell membrane. Mathematical models of the electrical and thermal fields that develop during the application of the pulses were used to design an efficient treatment protocol with minimal heating of the tissue. Tumor regression was confirmed by histological studies which also revealed that it occurred as a direct result of irreversible cell membrane permeabilization. Parametric studies show that the successful outcome of the procedure is related to the applied electric field strength, the total pulse duration as well as the temporal mode of delivery of the pulses. Our best results were obtained using plate electrodes to deliver across the tumor 80 pulses of 100 micros at 0.3 Hz with an electrical field magnitude of 2500 V/cm. These conditions induced complete regression in 12 out of 13 treated tumors, (92%), in the absence of tissue heating. Irreversible electroporation is thus a new effective modality for non-thermal tumor ablation.

Conflict of interest statement

Competing Interests: R. Davalos and B. Rubinsky have potential interests in the revenues of pending patents held by Univ. of California at Berkeley (e.g. No 10/571,162, Tissue Ablation with Irreversible Electroporation). B. Rubinsky also has a financial interest in Excellin Life Sciences and in Oncobionic, companies in the field of electroporation. L. M. Mir was a consultant for Oncobionics.

Figures

Figure 1. Determination of appropriate electrical parameters for an effective tumor treatment by IRE – experiments with immunocompetent mice.

Panels are identified by letters corresponding to the parameters described in table 1, except for panel A (tumor growth in untreated mice followed as controls of treatment conditions B and C), panel D (control of E and F), panel G (control of H and I) and panel J (control of K and L).

Figure 2. Determination of appropriate electrical parameters for an effective tumor treatment by IRE – experiments with immunodeficient (nude) mice.

Panels are identified by letters corresponding to the parameters described in table 1, except for panel A (tumor growth in untreated mice followed as controls of treatment conditions B and C) and panel D (control of treatments E and F).

Figure 3. Analysis of tumor evolution by HES histological staining after IRE.

A: control; B, C, D, E and F: respectively 1, 2, 6, 24 and 48 h after IRE.

Figure 4. TUNEL analysis at different times after the pulses delivery.

A: control; B, C and D: respectively 5 min and 1 and 24 h after IRE.

Figure 5. Immunohistochemical analysis of the tumour vasculature evolution by means of CD 31 staining in LPB tumors after treatment.

A: control; B, C and D: respectively 2, 6 and 24 h after IRE.