Chemoprevention of lung cancer

Chemoprevention is defined as the use of specific natural or pharmacologic agents to reverse, suppress, or prevent the carcinogenic process to the development of invasive cancer. The basic idea behind lung cancer chemoprevention is the concept that diffuse injury of the respiratory epithelium results from chronic carcinogen exposure. The rationale for chemoprevention arose from epidemiologic data demonstrating the existence of dietary inhibitors of carcinogenesis, basic studies of epithelial carcinogenesis, and laboratory evidence from animal models. Many of the studies evaluating specific agents focused on vitamin A and its synthetic analogs, the retinoids. Chemoprevention trials have investigated the effect of retinoids and other agents on bronchial metaplasia and dysplasia and sputum atypia; many of these trials have reported conflicting results. Several ongoing multi-institutional trials are evaluating chemoprevention regimens for prevention of second primary aerodigestive tract cancers, the results of which are eagerly awaited. Primary prevention trials to prevent lung cancer have reported sobering results, which negate the protective effects of beta-carotene against lung cancer development and provide no justification for consuming supplemental beta-carotene for cancer chemoprevention. In the future, the use of biomolecular markers as intermediate end points in chemoprevention trials may reduce the cost and time commitment required for these trials and aid in selecting a patient population that would benefit most from chemopreventive intervention or approaches such as gene therapy.