New research shows that 12,250 deaths per year could be delayed or averted if the United States screened healthy smokers nationwide for lung cancer CT, which is equivalent to 7.6 percent of all lung cancer deaths in the United States. The study, conducted by Dr. Jiemin Ma, senior epidemiologist in surveillance research at the American Cancer Society, and colleagues, used the most recent National Health Survey and 2010 U.S. Census data and the National Lung Screening Trial (NLST) patient criteria: patients were 55 to 74 years of age, smoked at least 30 packs per year, and either currently smoked or had quit smoking in the past 15 years. The NLST trial showed that low-dose CT (LDCT) screening reduced lung cancer mortality by 20% over 6.5 years compared with chest X-rays (N. Engl. J. Med. 2011;365:395-409). the NLST trial estimated that about 7 million Americans were suitable for LDCT screening, while the authors of this study estimated this number to be 8.6 million. A number of factors may have influenced the new estimate, including the use of the NLST-reported screening effect as a parameter to determine the number of avoidable lung cancer deaths. The authors suggest that while the direct use of the NLST screening effect has the advantage of simplicity and ease of understanding, it also allows the estimates in this study to be interpreted only within the framework of the NLST trial design and screening protocol. the NLST trial did not explore the effectiveness of screening in patients who smoked fewer than 30 packs per year or at an earlier age of smoking, and the 20% reduction in mortality in the LDCT screening group may have been underestimated. dr. Ma also noted that the NLST trial used chest X-rays (CXR) in the control group, which is unlikely to occur in the general population. If CXR was also effective in preventing lung cancer deaths, then this may also have led to an underestimation of the number of avoidable lung cancer deaths. Other factors that may lead to underestimation of mortality include the use of self-reported smoking data, which is less reliable because smokers tend to report lower levels of tobacco use than they actually do. On the other hand, the lung cancer mortality rate for the appropriate screening population was estimated based on the number of deaths from 2000 to 20006, which may overestimate the current mortality rate. The study model also assumes that 100% of the target population will be screened, which is unlikely to be achieved in reality. Under the ideal scenario of a 100% screening rate and a 30% reduction in lung cancer mortality, LDCT screening would prevent 18,375 lung cancer deaths per year. However, if only 70% of the 8.6 million eligible people were screened each year, the number of lung cancer deaths prevented would drop to 8,575. In an accompanying journal review, Dr. Larry Kessler, director of the University of Washington Health Services Center in Seattle, noted that 24.2 percent of LDCT screenings in the NLST trial were positive, and of those positive results, 96.4 percent were false positives. While the updated estimates reported in this study are important, the methodology used by the investigators is flawed. This study reports 1-year estimates rather than the more common life-saving/year values, which reflect the screening effect over time. This study may have underestimated the overall effect of the national CT screening program over time. In addition, various factors affecting smoking, such as age, menstruation, and cohort effects, were not explored in this study. There has been an alarming increase in the number of women who currently smoke, which would change the gender differences in lung cancer deaths. Among the 5.2 million men and 3.4 million women for whom screening was appropriate in this study, LDCT screening would have prevented 8,990 male deaths and 3,260 female deaths. This study was supported by the Internal Research Division of the American Cancer Society. both Dr. Ma and colleagues and Dr. Kessler declare no financial conflicts of interest.