The good news of a mortality benefit is tempered by some of the specifics. In the NLST, the number needed to screen to prevent 1 lung cancer death was 320 persons undergoing 3 annual LDCTs. Across all studies reviewed, the average rate of detecting nodules per round of screening was 20%, and more than 90% of these nodules turned out to be benign, leading to substantial follow-up testing including invasive procedures. Combining screening and follow-up diagnostic scans, the estimated mean 3-year radiation exposure of NLST participants in the screening group was 8 mSv, which Bach et al1 estimate would cause 1 cancer death per 2500 persons screened, although this death would likely occur many years later. The heterogeneity in nodule detection rate both among NLST sites and among the other studies reviewed by Bach et al,1 and the inconsistent mortality results of the 2 smaller RCTs, add a measure of uncertainty to the estimated benefit that would be obtained from broad application of LDCT screening. Nevertheless, the estimates of the benefits and risks of LDCT screening for lung cancer derived from the NLST are the best information currently available.