Initial results of the National Lung Cancer Screening Trial

The findings from the National Cancer Institute's National Lung Cancer Screening Trial (NLST) were recently published in the New England Journal of Medicine. The trial demonstrated that lung cancer mortality can be reduced by annual screening with low-dose computed tomography (CT). It is possible that widespread lung screening in high-risk groups can save many lives. Screening is associated not only with benefits but also possible harms. A number of observational single arm lung cancer screening trials with CT were carried out in the 1990s and during the past decade. These demonstrated that low-dose CT could identify cancers at early treatable stages and that survival was prolonged. The NLST was launched in 2002 and it is the first randomized controlled trial that has published definitive results. The trial included over 53,000 adults, aged 55–74 years, at high risk for lung cancer with at least a 30-pack-year history of smoking. It included current or former smokers. There were three rounds of annual CT screening. The control arm received three rounds of annual chest radiographs. The NLST demonstrated a 20% difference in lung cancer death rate between the CT arm and the chest radiograph arm with a 6.7% reduction in deaths from any cause. However, 40% of individuals in the CT arm experienced at least one abnormal CT scan during the study. Most of these abnormalities required only additional imaging (e.g. to determine if a nodule was growing) but some required more invasive procedures such as bronchoscopy or lung biopsy. A large percentage of abnormalities were false-positive readings. Such false-positive findings can lead to potential harm such as anxiety but also the additional costs of follow-up, radiation exposure and exposure to invasive procedures. In addition 7.5% of patients in the NLST study were judged to have a clinically significant abnormality other than an abnormality in the lungs, such as cardiac or upper abdominal findings. Additional publications from the NLST can be expected in the next year dealing with issues such as cost effectiveness and quality of life as well as radiation risk. In addition, many national societies are developing guidelines for lung cancer screening based on the preliminary results of the NLST.