Large Trial Finds Low Dose CT Lowers Lung Cancer Deaths in Heavy Smokers

The National Cancer Institute today released early findings from the National Lung Screening Trial (NLST), which show heavy smokers who were screened with low-dose spiral CT had 20 percent fewer deaths than smokers screened with chest X-ray. The NCI decided to announce the initial findings from the NLST after the trial’s independent Data and Safety Monitoring Board (DSMB) notified the NCI director that the data provided a statistically convincing answer to the study’s primary question and that the trial should therefore be stopped.  A fuller analysis, with more detailed results, will be prepared for publication in a peer-reviewed journal within the next few months.

The NLST is a prospective randomized clinical trial designed to determine the efficacy of lung cancer screening in smokers. In the NLST, investigators sought to determine if the mortality rate from lung cancer would be lowered in a group of long-term smokers who received a CT scan vs. those who receive a chest x-ray.  The American Cancer Society played a significant collaborative role in helping NCI achieve rapid recruitment into the NLST.

Below are comments from Otis W. Brawley, M.D., chief medical officer.

“The finding that a screening test reduces the risk of lung cancer death among people with a history of heavy smoking is an important one. The potential to save lives from lung cancer is a significant benefit and we look forward to the additional analyses of the study that will be forthcoming. As with any study of screening, there are also potential harms to be considered, such as potential overdiagnosis and needless surgeries. We have learned from the long-term analysis of other screening tests, such as mammography, that it is important to consider both benefit and harms associated with the test.

“That this finding occurs in a well designed prospective randomized trial is important, because it is most likely to give the correct answer. The NLST is an example of how to do good, responsible science. But we’ve also learned that promising initial results, even in large trials, are not always a sure bet. This study is strengthened by the fact that it showed the screening group had lower mortality from all causes, but we still must be cautious in interpreting the results before a full analysis is done.

“These findings will have people asking if our lung cancer screening recommendations are going to change and if so, when. Any time important new data are published, we take that evidence into account in our recommendations. For now, until this data and its analysis are published and the analysis and evidence are reviewed by independent experts, the best advice we can give is to encourage people to have conversations with their doctors about whether lung cancer screening is right for them.

“It is very important that this finding not weaken our efforts to reduce and eliminate tobacco use, which is the number one cause of lung cancer. Even if detecting lung cancer early reduces mortality, by far the best way to reduce deaths is by doing whatever we can to prevent the disease.

“The possible harms associated with CT scans include the effects of radiation from multiple scans; complications in patients who go through additional testing only to find they did not have lung cancer; and the possibility that patients will go through additional procedures that are actually not related to a potential finding of lung cancer. For instance, doctors may see signs of diseases they would otherwise not have known about, like liver or kidney disease.

“It should also be noted that the population enrolled in this study, while ethnically representative of the high-risk U.S. population of smokers, was a highly motivated and primarily urban group that was screened at major medical centers.  Thus the results may not accurately predict the effects of recommending low-dose helical CT scanning for other populations.

“Also, it’s important to remember that this finding applies only to persons at high risk of lung cancer due to a significant smoking history.  It does not address the issue of screening low risk patients, like never-smokers or people who smoked less than 30 pack years (smoking the equivalent of a pack per day for 30 years). We need to keep in mind there are risks from screening.  While this study demonstrates the benefits are greater than the risks for smokers, it does not address the issue in a low risk population. We need to consider that and guard against any unnecessary overuse of screening.”

About David Sampson

I am the director of medical and scientific communications for the American Cancer Society national home office.
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