Systems and method for destroying or inhibiting cancer cells and other rapidly-dividing cells include coupling an alternating polarity (AP) magnetic field generator to a target body area and applying an AP magnetic field having a frequency of 0.5-500 kHz and a field strength of 0.5-5 mT to the target body area to achieve a desired inhibiting effect on cancer cells or other rapidly-dividing cells. Treatments provided by the system may be co-administered with an anti-cancer drug such as a chemotherapy drug, a hormone therapy drug, targeted therapy drugs, immunotherapy drugs, or an angiogenesis inhibitor drug.