Lung cancer screening trials: Denmark and beyond.
Lung cancer is the leading cause of cancer death worldwide, with fewer than 15% of patients surviving 5 years after diagnosis, despite advances in treatment during the past 20 years. Lung cancer screening (secondary prevention), in addition to smoking cessation programs (primary prevention), might be the most exciting improvement in methods to reduce lung cancer mortality. The great interest in lung cancer screening was started by the introduction of low-dose multidetector computed tomography (CT) in the 1990s. The nonrandomized International Early Lung Cancer Action Project study (n 1⁄4 32,000) was followed by several randomized clinical trials of high-risk current and former smokers. These included the National Lung Screening Trial (NLST) in the United States (n 1⁄4 53,500), the DutchBelgian screening trial (n1⁄4 15,822), the Danish Lung Cancer Screening Trial (DLCST, n1⁄4 4104 ), and several other collaborating trials in Europe. Recently, the National Cancer Institute published the report that the NLST gave evidence for a mortality reduction of 20.3% with low-dose CT screening compared with chest radiographic screening and a 7% overall mortality reduction after 3 annual screening rounds and 8 years of follow-up. The NLSTwas a very well-performed randomized trial and has convincingly shown for the first time that CT screening, in high-risk subjects, can lead to a substantial reduction in lung cancer mortality and that the screening overall was not detrimental, because a reduction of 7% in general mortality was also observed. These are extremely important findings. The European trials have been smaller, but all have had a control group without any screening performed (usual care) and, therefore, potentially, the difference between the mortality in the CTand control arms could bemore pronounced. In addition, the trials were started 2 to 3 years after the NLSTand, therefore, have not yet performed a pooling of data and presented a combined mortality analysis. The Dutch-Belgian screening trial and theDLCSTare expected to perform afinal mortality analysis in 2015 but contemplated a preliminary pooling of data in 2011.