Abstract: The disclosure deals with methodologies and systems for oscillating electric fields (OEF), which can disrupt a cell's ability to divide. Passing these electric fields through, for example, a person's brain (or other anatomical organ or region of the body) possesses the ability to stop cancer cells from growing in patients where disease is expected. These devices can be worn by patients going through treatment to inhibit metastatic disease and to even enhance the sensitivity of established cancer cells to other therapies. Presently disclosed methodologies relate to varying frequency and/or amplitude of the oscillating electric signal for improved treatment effectiveness.