Chemoprevention in head and neck cancer: basic science and clinical application.

The concept of field cancerization and the multistep carcinogenesis theory are the premises on which the development of chemoprevention efforts has been based. The first concept underlies the fact that patients who have been cured of a cancer in the aerodigestive tract are still at risk of developing additional primary tumors in the same field, and the multistep carcinogenesis theory implies that the conceivable arrest of one of the steps by chemoprevention might be enough to impede the development of cancer. There is ongoing research for development of new candidate-chemopreventive substances in most areas of oncology. Most of the clinical experience in chemoprevention of head and neck cancer is based on the use of retinoids. Retinoids in high doses have demonstrated activity in treating oral premalignant lesions (OPLs) but with frequent side effects and early relapse after cessation of therapy. Subsequent trials showed better tolerability of retinoids in lower doses. Ongoing trials are currently evaluating whether chemoprevention over 3 years might have longer-lasting effect both on OPLs and in the prevention of second primary tumors.