Screening with low-dose
spiral CT scanning reduces lung cancer deaths by 20 percent compared
to chest x-ray
Current or heavy smokers who were screened
with low-dose spiral computed tomography (CT) scanning had a 20
percent reduction in deaths from lung cancer than did those who
were screened by chest X-ray, according to results from a decade-long,
large clinical trial that involved more than 53,000 people.
The study, called the National Lung Screening Trial (NLST), was
conducted in individuals at high risk of developing lung cancer
to compare the differences in death rates between smokers aged 55
to 74 who were screened annually with low-dose helical (or spiral)
CT, versus the conventional chest X-ray.
The study results were published June 29, 2011 in the early online
edition of the peer-reviewed New England Journal of Medicine.
Dr. Denise R. Aberle, national principal investigator for 23 of
the 33 NLST sites and a researcher with UCLA's Jonsson Comprehensive
Cancer Center, said this publication provides a more extensive analysis
of the data than was initially reported in November 2010, and offers
further definitive evidence of a significant mortality benefit from
CT screening.
"These findings confirm that low dose CT screening can decrease
deaths from lung cancer, which is expected to kill more than 150,000
Americans this year alone," said Aberle, who serves as vice
chair for research in the Department of Radiological Sciences. "This
study also will provide us with a road map for public policy development
in terms of lung cancer screening in the years to come."
Beginning in August 2002, the NLST enrolled 53,454 men and women.
Participants had either a current or former cigarette smoking history
of at least 30 pack-years, and had to be without symptoms or a history
of lung cancer. 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.
Participants were randomly assigned to receive three annual screenings
with either the low-dose spiral CT or the standard chest X-ray.
Spiral CT uses X-rays to obtain multiple "slices" through
the entire chest cavity during a seven- to 15-second breath-hold.
A standard chest X-ray requires only a sub-second breath-hold, but
produces just a single image of the whole chest in which anatomic
structures overlie one another, perhaps obscuring a potential malignancy.
Previous studies to determine whether standard chest X-ray examinations
can reduce lung cancer mortality have not been successful, primarily
because of the small numbers of participants enrolled. The NLST
is the first trial with sufficient numbers of participants using
a randomized design to enable the comparison of mortality differences
between spiral CT and chest X-ray, Aberle said.
Sponsored by the National Cancer Institute, part of the National
Institutes of Health, the NLST establishes low-dose spiral CT as
the first validated screening test that reduces lung cancer mortality.
Aberle said that while the results are very encouraging and should
re-shape screening guidelines in the future, CT screening is not
an alternative to smoking cessation. The best and most effective
way to reduce lung cancer deaths is for smokers to quit and for
those who don't smoke to refrain from starting.
One of the major limitations of CT screening is the number of screens
in which a nodule or other indeterminate finding potentially related
to lung cancer is found.
"These abnormal findings usually require some form of additional
diagnostic evaluation, including invasive procedures that carry
their own risks," Aberle said. "Although these 'false
positive' screens were seen in about 24% of all CT scans in the
study, follow-up of individuals showed that complications from both
screening examinations and downstream diagnostic testing were low."
In addition to collecting detailed information about the imaging
screenings and other clinical information, UCLA's Jonsson Comprehensive
Cancer Center and a subset of NLST sites collected and banked specimens
of blood, sputum, and urine at each of the three screening time
points. Resected tumor tissues from lung cancer patients who underwent
surgical resection were also collected across most sites. These
specimens will provide a rich resource to validate molecular markers
that may compliment imaging to detect early lung cancer, Aberle
said.
More studies based on the NLST data set are ongoing, and will include
reports on the cost effectiveness of spiral CT and the effects of
the screening process on smoking behaviors over time.
The NLST was designed to answer specific questions about the screening
in older heavy smokers and was conducted at sites with sophisticated
medical resources and experts.
"The NLST cannot answer all of the important questions about
screening that will be important for implementation," Aberle
said. "However, the NLST data can be used to develop mathematical
models to determine how long screening should be performed and how
often. In addition, the data can be used to determine whether other
groups at risk of lung cancer, such as light smokers, those with
family histories of lung cancer or individuals with lung diseases
like emphysema, would benefit from screening with spiral CT scanning."
The NLST was conducted by the American College of Radiology Imaging
Network, an imaging research network that conducts multi-center
clinical trials, and the Lung Screening Study group, initially established
by the National Cancer Institute to examine the feasibility of the
NLST.
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