Preclinical and clinical models of lung cancer chemoprevention.

In smokers, beta-carotene, retinol, and vitamins E and C appear to have little or a negative effect against human lung cancer development. Similarly, these chemicals have generally failed to inhibit lung tumorigenesis in rodents. The agents that have been shown to inhibit lung tumorigenesis in rodents, such as glucocorticoids, green tea, NSAIDs, and isothiocyanates, have not been tested yet in humans. These agents may be more effective in preventing human lung cancer in smokers than are the chemicals tested so far, especially if they are delivered by inhalation route.