The basic principle of electric field therapy (also tumor treating fields) is similar to some chemotherapeutic drugs. It blocks the ability of tumor cells to divide by disrupting the normal function of the mitotic spindle. Hence it targets rapidly dividing tumor cells. When exposed to these fields during mitosis, cells suffer from violent membrane blebbing and disruption of microtubule spindle elements and chromosomal order. Mitotic disruption specifically occurs at the end of metaphase and the beginning of anaphase (dividing of chromosomes). [1]

figure: Mitosis. Electric field therapy leads to disruption of metaphase and anaphase [2]

Bibliography

1)  Swanson K.D. (2016) An Overview of Alternating Electric Fields Therapy (NovoTTF Therapy) for the Treatment of Malignant Glioma, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4703612/

2) mitosisdetail.jpg, https://smartsite.ucdavis.edu/access/content/user/00002950/courses/sites/cknamed/mitosisdetail.jpg (access 29/05/17)