BACKGROUND: Lung cancer is the leading cause of cancer-related death in the United States. Because early-stage lung cancer is associated with lower mortality than late-stage disease, early detection and treatment may be beneficial.
PURPOSE: To update the 2004 review of screening for lung cancer for the U.S. Preventive Services Task Force, focusing on screening with low-dose computed tomography (LDCT).
DATA SOURCES: MEDLINE (2000 to 31 May 2013), the Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews (through the fourth quarter of 2012), Scopus, and reference lists.
STUDY SELECTION: English-language randomized, controlled trials or cohort studies that evaluated LDCT screening for lung cancer.
DATA EXTRACTION: One reviewer extracted study data about participants, design, analysis, follow-up, and results, and a second reviewer checked extractions. Two reviewers rated study quality using established criteria.
DATA SYNTHESIS: Four trials reported results of LDCT screening among patients with smoking exposure. One large good-quality trial reported that screening was associated with significant reductions in lung cancer (20%) and all-cause (6.7%) mortality. Three small European trials showed no benefit of screening. Harms included radiation exposure, overdiagnosis, and a high rate of false-positive findings that typically were resolved with further imaging. Smoking cessation was not affected. Incidental findings were common.
LIMITATIONS: Three trials were underpowered and of insufficient duration to evaluate screening effectiveness. Overdiagnosis, an important harm of screening, is of uncertain magnitude. No studies reported results in women or minority populations.
CONCLUSION: Strong evidence shows that LDCT screening can reduce lung cancer and all-cause mortality. The harms associated with screening must be balanced with the benefits.
PRIMARY FUNDING SOURCE: Agency for Healthcare Research and Quality.
The "cost" of low-dose CT lung cancer screening is the incredibly large false-positive rate. But no other screening for any disease has shown a reduction in all-cause mortality, and no other screening test has a number needed to screen approaching 300 for reduction of cause-specific mortality. Caution is needed though because not all centers have LOW-DOSE protocols or equipment. These trials specifically used LOW radiation doses. We should not be exposing patients to the remarkably high radiation doses of standard chest CT scans for screening. AND we should not screen a patient who has recently had a diagnostic standard chest CT where no suspicious lesions for lung cancer were found. I think we need a national registry where the results of every chest CT are readily available and no screening CT is done without first seeing whether the patient just had a chest CT in their emergency room.
With only 4 RCTs of lung cancer screening by CT scan, this evidence review collapses to a review of the NSLT study because of the small size and other limitations of three of the studies. Those already familiar with NSLT can skip this paper unless they are interested in learning about the limitations of the three small European studies.
The news isn`t new. The findings now have further follow-up and more clarity of benefit in both lung cancer and overall mortality reduction. The continuing upset is over "false positives" and "anxiety" and cost and mortality. The search will be on for cheaper means and molecular markers that achieve the same goals at lesser costs.
Systematic review finding that there is good evidence for CT screening to detect lung cancer. The conclusions are based primarily on the one large trial to date, the results of which are already well known.
Screening chest CT scans for lung cancer will become standard of care in the very near future. The medical community needs to prepare for the implications, not only of more patients with early stage lung cancer, but the increased number of false-positive lesions identified with screening.