The presence of any emphysema on CT scans and the risk of lung cancer. Emphysema was assessed on a semiquantitative visual scale. RR = relative risk.

The relationship between LAA on CT scans and the risk of lung cancer. LAA = low attenuation area; WMD = weighted mean difference.

Proposed schema for lung cancer screening using CT scan. Based on the National Lung Screening Trial data, we propose that screening programs target smokers 55 to 74 years of age with at least 30 pack-years of smoking history. In addition, we suggest incorporating spirometry data to a risk stratification algorithm for the initial screening CT scan, especially in men. All suspicious nodules should be investigated. For those without significant nodules, we suggest evaluating the CT scan for emphysema by a trained radiologist. Even trace findings of emphysema should prompt additional screening studies. The absence of emphysema, on the other hand, may lead to fewer screening CT scans. Those with nodules between 4 and 10 mm may require more frequent CT scan follow-up.