CT Screening Significantly Reduces Lung Cancer Mortality
Posted Nov 22 2010 1:01pm
A low-dose CT scan can detect lung cancers at relatively early
stages and reduce deaths from lung cancer by as much as 20%,
according to a new study. The trial was halted early because
of the positive results.
Lung cancer, which is mostly caused by cigarette smoking, is
the leading cause of cancer-related deaths in the United States.
The majority of cases arent detected until symptoms appear.
By then, in up to 30% of patients, the disease has spread outside
the lungs and is much more difficult to treat.
Researchers have been working to develop methods for identifying
lung cancer before symptoms appear. Standard chest X-rays, which
produce a single image of the entire chest, can detect tumors
greater than 1 cm in size. But there's no evidence that standard
chest X-ray exams can reduce lung cancer mortality.
Low-dose helical computed tomography (LDCT)—also called
spiral CT—uses X-rays to capture multiple images on a computer.
It can detect tumors significantly under 1 cm in size, but studies
havent yet shown whether LDCT screening can reduce lung cancer
death rates. The National Lung Screening Trial, funded by NIHs
National Cancer Institute (NCI), set out to compare LDCT with
standard chest X-rays in people at high risk for developing lung
cancer. The study design and protocol were described in the online
edition of Radiology on November 2, 2010.
Researchers at 33 trial sites nationwide enrolled over 53,000
current or former smokers without signs, symptoms or a history
of lung cancer. The participants were randomly assigned to receive
3 annual screens with either LDCT or a standard chest X-ray.
They were then followed for up to another 5 years. All deaths
were documented, with special attention given to the verification
of lung cancer as a cause of death.
On October 20, 2010, the studys independent Data and Safety
Monitoring Board voted unanimously to stop the trial. By that
time, there were 354 deaths from lung cancer in the LDCT arm
of the study, compared to a significantly larger 442 lung cancer
deaths in the chest X-ray group. The Board concluded that this
20.3% reduction in lung cancer mortality met the standard for
statistical significance. They also found no evidence of unforeseen
"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," says Dr. Christine Berg, the NCI
project officer for the study.
The researchers also found that all-cause mortality—death
due to any factor, including lung cancer—was 7% lower in
the LDCT group. Over half of this difference came from a decrease
in lung cancer deaths. The researchers will need to analyze the
data further to better understand this and other aspects of the
While NCI has posted the preliminary results online, a fuller
analysis with more detailed results will be prepared for publication
in a peer-reviewed journal within the next few months.