Throughout human life the immune system is able to identify and attack aberrant cells which if not contained become cancerous. The method of attack is to use free radicals, free electrons with a negative charge, and they are attracted to the aberrant cells which have a positive outer cell membrane charge. The free radicals are capable of destroying the cancer cells and arrest any further development of new cancer cells. It's not the process of a few cancer cells that are lethal to humans but it's the process of uncontrolled replication, use of available nutrients obtained via the blood supply and the removal of waste from the rapid growing cancer cells. By checking the growth the process we know as cancer is prevented and that is the normal course of life for most people.
For reasons still unknown it appears the aberrant cells evolve into new cells that the immune system can not find and attack. The mechanism of doing this is a reversal of polarity on the outer cell wall membrane from a positive potential to a negative potential. In physics we know that like charges repel and unlike charges attract. The simple analogy is putting two bar magnets together and if opposite ends they attract and bind, if same ends (north pole/north pole) then they repel or push away. The electromagnetic forces of the negative and positive polarities of the end of the bar magnet determine the course of action. Over time possibly through evolution of survival by pre-cancerous cells the change of polarity from positive to negative prevents the immune system from attacking and destroying thus cells become cancerous and death and disease result.
It seems reasonable that if one can use external electrical devices of specific polarities and strengths then some of these cells can be repulsed or removed from the body by physical stimulation using electrotherapy. The dosage and duration of the treatments has not been determined or tried to the author's knowledge but from a quantum physics angle of the use of polarities it would appear any cell resistances can be overcome by an external device.
Cancer is too devastating to not be investigating all potential therapies, including physical ones.