The NSAID, sulindac and/or its metabolites and derivatives, in combination with hydrogen peroxide or another oxidizing agent, such as arsenic trioxide that generates reactive oxygen species (ROS), significantly enhances the killing of cancer cells. This effect occurs at concentrations of each compound that individually have little or no activity directed against cancer cells. A skin cream has been developed and used to treat skin cancer and precancerous skin growths that effectively removes the lesions with no effect on surrounding normal skin.