Importance of tumour coverage by sufficiently high local electric field for effective electrochemotherapy

Electrochemotherapy is an effective local treatment of solid tumours which combines delivery of chemotherapeutic drug and electric pulses. Electric pulses increase permeability of plasma membrane transiently and reversibly, leading to increased transport of the drug into the cell. As all clonogenic cells in the tumour need to be eradicated for effective treatment, all cells have to be permeabilised, i.e. all cells in the tumour have to be exposed to appropriate electric pulses. Electric pulses are delivered to tissue by electric pulses generator via electrodes. In general there are two types of electrodes, plate electrodes and needle electrodes. The target tissue, i.e. tumour, is to be positioned well in-between the electrodes. The electrodes should thus fit the size of the tumour for good electric field distribution. Plate electrodes which are noninvasive are better suited for tumours on the surface on the skin, whereas needle electrodes which are used invasively with appropriate and sufficient depth of their insertion are more appropriate for treating tumours seeded deeper in the skin.