A large randomized national trial has provided the first evidence of a significant reduction in lung cancer deaths with a screening test.
The National Lung Screening Trial (NLST) reported a 20.3% reduction in lung cancer mortality among heavy smokers screened with low-dose helical computed tomography (CT), as compared with those given standard chest x-rays. The trial enrolled more than 53,000 older, high-risk individuals.
In addition, deaths from any cause, including lung cancer, were 7% lower among participants screened with low-dose helical CT, also known as spiral CT.
The initial results were released today by the study sponsor, the National Cancer Institute, after the study's independent data and safety monitoring board recommended halting the trial.
“The fact that low-dose helical CT provides a decided benefit is a result that will have implications for screening and management of lung cancer for many years to come,” Dr. Christine Berg, project officer for the lung screening study at the NCI, said in a statement.
Beginning in 2002, the NLST recruited about 53,500 American men and women, aged 55-74 years, who were current or former smokers with a smoking history of at least 30 pack-years. It randomly assigned them to receive three annual screens with low-dose helical CT or chest x-ray. Helical CT uses x-rays to obtain a multiple-image scan of the entire chest during a 7- to 15-second breath-hold, whereas a standard chest x-ray produces only a single image of the chest from a sub-second breath-hold.
At the time of the Oct. 20, 2010 analysis, 354 deaths from lung cancer had occurred in the CT arm vs. 442 in the chest x-ray group. Approximately 25% of deaths in the NLST were due to lung cancer.
NCI director Harold E. Varmus said the well-designed study used rigorous scientific methods and that its findings could spare countless lives.
“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% has the potential to spare very significant numbers of people from the ravages of this disease,” he said. “But these findings should in no way distract us from continued effort to curtail the use of tobacco, which will remain the major causative factor for lung cancer and several other diseases.”
Like other screening strategies, the use of low-dose helical CT has disadvantages including the cumulative effects of radiation from multiple CT scans, complications among patients who need additional testing to make a definitive lung cancer diagnosis, and the anxiety and added cost associated with investigating incidental findings picked up on CT.
[Editor's note: In 2009, investigators reported that low-dose CT screening was associated with twice the rate of false positives and more unneeded interventions, compared with chest x-ray, in a randomized feasibility trial that preceded the NLST. But low-dose CT also detected twice as many lung cancers as did chest x-ray screens in that study.]
Although the NLST trial cohort was ethnically representative of the high-risk U.S. population, the researchers noted that participants were highly motivated and screened at major medical centers. Thus, the results may not accurately predict the effect of CT screening for other populations.
“What has happened here is that the technology shows you can cut down on lung cancer deaths, the leading cause of cancer mortality, and save nearly as many lives as the number of people who die from breast cancer per year. We as a medical community now need to figure out how to do this in a way that the cost is acceptable to the public,” Dr. Bruce E. Johnson, an official with the American Society of Clinical Oncology and director of the Lowe Center for Thoracic Oncology at the Dana-Farber Cancer Institute in Boston, said in a statement.
A more detailed analysis of the NLST results is expected to be published in the coming months, although a paper describing its design and protocol was published by the journal Radiology.
The National Cancer Institute sponsored the study.