Recent data suggests that
retinoids and
carotenoids may be effective in reversing a putative "field cancerization" defect in the epithelium at risk for
oral cancer. Animal experiments have shown that these compounds can inhibit
cancer formation. Several clinical trials have demonstrated the ability of
retinoids to reverse
oral leukoplakia. However, toxicities associated with
retinoids at the doses used in these studies limits their potential for
chemoprevention. Because of its lack of toxicity,
beta-carotene is a very attractive agent for
chemoprevention. It suppresses micronuclei in exfoliated oral mucosal cells from subjects at risk for
oral cancer and recently has been shown to be active in reversing
leukoplakia. Another area under investigation is the possibility of preventing second primary
tumors in patients cured of their initial
cancer who have an increased risk of developing new
cancers of the upper acrodigestive tract.