Applying the National Lung Screening Trial eligibility criteria to the US population: what percent of the population and of incident lung cancers would be covered?

The National Lung Screening Trial (NLST) demonstrated a 20% reduction in lung cancer mortality for screening with low-dose computed tomography versus chest radiography. The major NLST eligibility criteria were age 55-74, a 30 + pack year smoking history and current smoking status or having quit in the last 15 years. We utilized data from SEER (Surveillance, Epidemiology and End Results), the United States (US) Census and the National Health Interview Survey, as well as two statistical models of lung cancer risk, to estimate the proportion of the total US population and of those currently diagnosed with lung cancer that would be covered by the NLST and other suggested eligibility criteria. For the NLST criteria, 26.7% of lung cancers and 6.2% of the population (over 40) were covered. A criterion of ever smokers aged 50-79 would cover 68% of the cancers while screening 30% of the (over 40) population. To extend recommended screening beyond the NLST eligibility criteria, two questions are key. First, can the 20% mortality reduction observed in NLST be extrapolated to populations at moderately lower risk? Second, given that such an extrapolation is valid, what background incidence rate is high enough for the balance between the benefits and harms of screening to be favourable? Further research on these questions is needed.