STUDY SUMMARY
Broader eligibility for screening supports mortality benefit
This is an update to the 2013 clinical practice guideline on lung cancer screening. The USPSTF used 2 methods to provide the best possible evidence for the recommendations. The first method was a systematic review of the accuracy of screening for lung cancer with LDCT, evaluating both the benefits and harms of lung cancer screening. The systematic review examined various subgroups, the number and/or frequency of LDCT scans, and various approaches to reducing false-positive results. In addition to the systematic review, they used collaborative modeling studies to determine the optimal age for beginning and ending screening, the optimal screening interval, and the relative benefits and harms of various screening strategies. These modeling studies complemented the evidence review.
The review included 7 randomized controlled trials (RCTs), plus the modeling studies. Only the National Lung Screening Trial (NLST; N = 53,454) and the Nederlands-Leuvens Longkanker Screenings Onderzoek (NELSON) trial (N = 15,792) had adequate power to detect a mortality benefit from screening (NLST: relative risk reduction = 16%; 95% CI, 5%-25%; NELSON: incidence rate ratio = 0.75; 95% CI, 0.61-0.90) compared with no screening.
Screening intervals, from the NLST and NELSON trials as well as the modeling studies, revealed the greatest benefit from annual screening (statistics not shared). Evidence also showed that screening those with lighter smoking histories (< 30 pack-years) and at an earlier age (age 50) provided increased mortality benefit. No evidence was found for a benefit of screening past 80 years of age. The modeling studies concluded that the 2013 USPSTF screening program, using a starting age of 55 and a 30-pack-year smoking history, would reduce mortality by 9.8%, but by changing to a starting age of 50, a 20-pack-year smoking history, and annual screening, the mortality benefit was increased to 13%.1,11
Comparison with computer-based risk prediction models from the Cancer Intervention and Surveillance Modeling Network (CISNET) revealed insufficient evidence at this time to show that prediction model–based screening offered any benefit beyond that of the age and smoking history risk factor model.
The incidence of false-positive results was > 25% in the NLST at baseline and at 1 year. Use of a classification system such as the Lung Imaging Reporting and Data System (Lung-RADS) could reduce that from 26.6% to 12.8%.2 Another potential harm from LDCT screening is radiation exposure. Evidence from several RCTs and cohort studies showed the exposure from 1 LDCT scan to be 0.65 to 2.36 mSv, whereas the annual background radiation in the United States is 2.4 mSv. The modeling studies estimated that there would be 1 death caused by LDCT for every 18.5 cancer deaths avoided.1,11
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