Low-dose spiral CT scans are associated with 20.3% fewer deaths from lung cancer compared to chest X-rays, the NCI (National Cancer Institute) has announced. The CT (computed tomography) devices are able to identify lung cancer at an earlier stage than X-rays.
The American College of Radiology Imaging Network (ACERIN) and the Lung Screening Study group carried out a randomized trial involving 53,500 heavy current and ex-smokers aged between 55 and 74, called the NLST (National Lung Screening Trial), and compared the impact of low-dose helical CT (computed tomography) against chest X-rays on lung cancer mortality. It found that those screened with the low-dose helical CT have a 20.3% lower risk of dying from lung cancer.
The National Cancer Institute (NCI), which sponsored the trial, is part of the NIH (National Institutes of Health).
You can read about this trial and its findings in the medical journal Radiology. Harold Varmus, M.D., NCI Director, said:
This large and well-designed study used rigorous scientific methods to test ways to prevent death from lung cancer by screening patients at especially high risk. Lung cancer is the leading cause of cancer mortality in the U.S. and throughout the world, so a validated approach that can reduce lung cancer mortality by even 20 percent has the potential to spare very significant numbers of people from the ravages of this disease. But these findings should in no way distract us from continued efforts to curtail the use of tobacco, which will remain the major causative factor for lung cancer and several other diseases.
The trial’s independent Data and Safety Monitoring Board said the study should be stopped because the “accumulated data now provide a statistically convincing answer to the study’s primary question”.
The NCI says that a fuller report on the findings will be published in a few months’ time. All trial participants are being written to by the study’s researchers regarding the findings, which can be viewed here.
53,000 males and females were enrolled by the NLST in August 2002 at 33 centers around the USA – the trial lasted 20 months. All participants, either current or ex-smokers, had a 30 pack-years history and had no history of lung cancer or signs/symptoms of the disease. According to the NCI, “pack-years are calculated by multiplying the average number of packs of cigarettes smoked per day by the number of years a person has smoked.” They were selected at random to receive either low-dose helical CT or standard chest X-rays annually for three years.
A helical CT utilizes X-rays to get a multiple-image scan of the whole chest while the patient holds his/her breath for 7-15 seconds. During a standard chest X-ray patients only need to hold their breath for a fraction of a second, and a single image of the entire chest is created.
The researchers informed that previous studies aimed at proving that standard chest X-ray examinations could lower lung cancer mortality had failed.
The participants were screened three times – when they first enrolled, one year later, and a year after that. They were then followed-up for five years. The researchers documented all deaths, and took special note of deaths caused by lung cancer.
When the Data and Safety Monitoring Board (DSMB) had its final meeting (October 20, 2010), 354 participants who had received CT scans had died of lung cancer, compared to 442 in the chest X-ray group. The DSMB recommended ending the study because the CT screening’s 20.3% reduction in lung cancer mortality was statistically significant.
Christine Berg, M.D., NLST project officer for the Lung Screening Study at NCI, said:
This is the first time that we have seen clear evidence of a significant reduction in lung cancer mortality with a screening test in a randomized controlled trial. The fact that low-dose helical CT provides a decided benefit is a result that will have implications for the screening and management of lung cancer for many years to come.”
The trial also found that all-cause mortality was 7% less in the helical CT group compared to the standard chest X-ray group. All-cause mortality refers to deaths due to any factor, as well as lung cancer. About 25% of deaths in the NLST were caused by lung cancer. Factors, such as cardiovascular disease caused the other deaths. The researchers say further studies are needed to examine these additional findings.
Denise Aberle, M.D., NLST national principal investigator for ACRIN, said:
The results of this trial provide objective evidence of the benefits of low-dose helical CT screening in an older, high-risk population and suggest that if low-dose helical CT screening is implemented responsibly, and individuals with abnormalities are judiciously followed, we have the potential to save thousands of lives. However, given the high association between lung cancer and cigarette smoking, the trial investigators re-emphasize that the single best way to prevent lung cancer deaths is to never start smoking, and if already smoking, to quit permanently.
The researchers say helical CT scanning does have some disadvantages, such as the radiation effects of multiple CT scans, complications in patients who are found not to have lung cancer but require further testing, as well as risks from additional diagnostic work-up for findings not related to potential lung cancer, such as kidney or liver disease.
Screening, in itself, increasing the risk of suspicious findings that are eventually found not to be cancer in many cases – these have a financial toll, as well as producing anxiety. All these disadvantages have to be balanced against the considerable drop in lung cancer mortality.
“The National Lung Screening Trial: Overview and Study Design”
National Lung Screening Trial Research Team
Radiology November 2, 2010, doi: 10.1148/radiol.10091808
Written by Christian Nordqvist