[Selenium and oral cancer. Review of the literature]

During normal cellular metabolism, free oxygen radicals are constantly generated. These are extremely toxic. However, they are rapidly eliminated by a series of metabolic steps, which involve certain enzymes such as superoxide dismutase, catalase and glutathione peroxidase (a selenium dependent enzyme). The toxic effect of free oxygen radicals has been suggested to have carcinogenic properties, and this hypothesis may be the link between low selenium levels and increased cancer morbidity. From this point of view a correct selenium concentration in the plasma may represent a form of chemioprevention. In fact, the concept of chemioprevention of carcinogenesis with inhibitory chemical compounds is particularly apropous to head and neck squamous cell cancer control, because the incidence of metachronous second primary tumours in surviving patients with oral cancer is very high.