The present invention provides devices and systems, as well as methods, of electric field delivery and non-thermal or mild hyperthermia, and preferential or selective ablation of cancerous cells of target tissue regions. A method can include, for example, advancing a probe comprising a plurality of electrodes to a target tissue region comprising cancerous cells, and deploying the plurality of electrodes from a distal portion of a probe, and applying an alternating current so as to provide one or more electric fields extending through the volume and selectively or preferentially destroy cancerous cells within the volume.