Lung cancer is the most common fatal type of cancer in the developed world. The overwhelming majority of cases of lung cancer are caused by tobacco products (1) , and even with the best therapeutic approaches, less than 15% of diagnosed cases survive 5 years (2) . It has been noted that even after smoking cessation, the risk of lung cancer remains elevated for over 15 years (3) . This observation clearly indicates that lung cancer has a protracted course developing over a 10-20-yr period, from the moment in which an epithelial cell becomes initiated by chronic exposure to chemical insults until a clinically evident cancer is detected. The long latency period generated by this biology provides an important window of opportunity to find transformed precancerous cells in high-risk populations and intervene in a timely manner.
