The spreading of cancer cells in a target region can be inhibited by imposing a first AC electric field in the target region for a first interval of time, with a frequency and amplitude selected to disrupt mitosis of the cancer cells; and imposing a second AC electric field in the target region for a second interval of time, with a frequency and the amplitude selected to reduce motility of the cancer cells. The amplitude of the second AC electric field is lower than the amplitude of the first AC electric field.