Chemoprevention of respiratory tract cancer

Lung cancer is the leading cause of cancer death in the United States, and advances in therapy have accounted for an improvement in five-year survival in this disease from 9% to 13% over the last three decades. Molecular genetic evidence has confirmed the epidemiologic link between tobacco and lung cancer causation, and has clarified the etiology of the persistent risk of lung cancer development in former smokers. Retinoids have shown promise in aerodigestive cancer chemoprevention, both in the reversal of preneoplastic lesions and in the prevention of second primary cancers. After initial epidemiologic and dietary studies had linked β-Carotene with cancer risk reduction, large randomized phase III studies of this compound have shown no evidence of benefit and some evidence of heightened lung cancer risk in active smokers on high dose supplemental β-Carotene. Therefore, careful clinical, epidemiologic, and basic studies of retinoids using intermediate end point markers are necessary to determine the definitive role of these compounds in the chemoprevention of respiratory tract cancer, with a particular focus on former smokers.