Medical devices for treatment of cancer with electric fields

A medical device comprising:

• an electric field generating circuit configured to generate two or more electric fields;
• and
• control circuitry in communication with the electric field generating circuit, the control circuitry configured to control delivery of the two or more electric fields from the electric field generating circuit;
• and
• one or more leads in electrical communication with the electric field generating circuit, wherein each of the one or more leads comprise four or more electrodes disposed along a length of each of the one or more leads;
• wherein the control circuitry causes the electric field generating circuit to generate the two or more electric fields at frequencies selected from a range of between 10 kHz to 1 MHz at a site of a cancerous tumor located within a bodily tissue, wherein the two or more electric fields are effective to prevent and/or disrupt cellular mitosis in a cancerous cell;
• wherein the two or more electric fields are delivered along more than one vector between at least two pairs of the four or more electrodes surrounding the cancerous tumor, wherein a first pair of the four or more electrodes is positioned between a second pair of the four or more electrodes such that the second pair of the four or more electrodes has a broader electric field reach than the first pair of the four or more electrodes;
• and
• wherein the control circuitry is further configured to generate the two or more electric fields having an electrical waveform alternating between positive pulses and negative pulses, the waveform including one or more OFF time periods between at least some adjacent positive and negative pulses, wherein the positive pulses and negative pulses are relative to a bias voltage between −5 V and 5 V and the one or more OFF time periods is defined by an electrical potential equal to the bias voltage.