Methods for treating cancers, tumors, and neoplasms using a composition comprising one or more generally regarded as safe (GRAS) compounds selected from the group of components consisting of vitamins, selenium, fatty acids, fatty acid salts, and fatty acid esters, and mixtures of two or more said components, either as a stand-alone treatment or in combination with one or more anti-cancer drugs or devices or other anti-neoplastic agents, treatments, or devices are provided. In some instances, concomitant hyperthermia therapy is employed. Also provided are compositions and kits containing the compositions, for implement various aspects of the invention.