Lung Cancer Trial Results Show Mortality Benefit With Low-Dose CT
National Institutes of Health/National Cancer Institute [press release]
November 4, 2010. Available at: https://www.nih.gov/news/health/nov2010/nci-04.htm
The National Cancer Institute (NCI) released initial results of a trial of screening methods to detect early lung cancer and thus reduce lung cancer mortality. The trial, known as the National Lung Screening Trial (NLST), was a randomized multicenter study comparing low-dose helical CT with conventional chest radiography in 53,000 current and former smokers age 55 to 75 years. The primary endpoint was lung cancer mortality. Enrollment was completed in 2004. Each participant received a baseline and 2 annual screenings after being randomly assigned to 1 of the above screening methods. Follow-ups were maintained for another 5 years. Participants were informed of any abnormal findings.
The trial was discontinued when the independent Data and Safety Monitoring Board found that a predetermined statistically convincing outcome had been reached. This was a 20.3% reduction in lung cancer mortality among participants in the CT arm compared with mortality in the conventional chest radiography arm (354 vs 442 deaths, respectively). Lung cancers accounted for approximately one quarter of all mortalities in each arm, and the all-cause mortality was also 7% lower in the CT arm. Explanations for the latter finding will be sought in further examination of the data.
Because of the enormous toll of lung cancer, the NCI predicts that 157,000 lung cancer deaths will occur in 2010. Screening for lung cancer has been attempted many times. Screening methods have included routine chest x-rays, sputum cytology, and even bronchoscopy. None has provided any evidence that lung cancer mortality was reduced.[23,24,25] Although some lung cancers were detected at early stages by some screening interventions, mortality was not significantly improved by early detection. Nearly 30 years ago, the NCI discontinued its recommendation to perform routine annual chest x-rays in smokers. However, radiologic technology has advanced very considerably in recent decades, so the NLST was launched to re-examine the possibility that early detection with modern technology could finally reduce lung cancer mortality. The choice of mortality as the primary endpoint in the NLST was robust, given the previous experience that early detection per se did not reduce the eventual mortality.
The finding that lung cancer mortality was reduced by 20% in the trial is most welcome and, if verified after complete review of the data, has the potential to save more than 30,000 lives per year in the United States alone. Nevertheless, some concerns remain. One concern is that multiple CT scans entail cumulative radiation exposure, which, although not as much as that from previous radiologic techniques, is not negligible. A second concern is that some abnormalities will turn out to be benign lesions that would otherwise have gone undetected and uninvestigated. This could result in anxiety, unnecessary invasive procedures, and expense. These concerns will need to be weighed against the advantage of early detection and possible curative treatment of one of the most deadly and common malignancies. Full reports of the trial will be available early in 2011. The recommendation to start annual helical CT screening of current and former smokers cannot yet be made but seems likely after due deliberation.
Although most welcome, the result of this well-designed and conducted trial in no way reduces the need to avoid the risks for lung cancer, particularly those related to smoking.
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