Lung Cancer Screening with Low-Dose CT Produces
False diagnosis may cause additional cost, anxiety,
and sometimes death from cancer treatment
See information below news report on
CT scans and lung cancer
Dec. 9, 2013 – More than 18 percent of all lung
cancers detected by low-dose computed tomography (LDCT) appeared to
represent an overdiagnosis, according to a study of patients between the
ages of 55 and 74 years published by JAMA Internal Medicine, a
JAMA Network publication.Overdiagnosis cases represent an important potential harm because
they incur additional cost, anxiety, and death associated with cancer
LDCT has been shown in recent clinical trials to be
an effective screening tool in some patients, but some of the tumors it
finds may be indolent (slow growing) or clinically insignificant.
Overdiagnosis is the detection of a cancer with a screening test that
wouldn’t otherwise have become clinically apparent. It is a potential
harm of screening because of the additional cost, anxiety and
complications associated with unnecessary treatment, according to the
Radiographic imaging exposes relationship between
obesity and cancer in aging population; women with more overall fat
mass, more visceral fat had a higher risk of cancer; fat puts older men
at risk even with healthy BMI
Edward F. Patz Jr., M.D., of Duke University
Medical Center, Durham, N.C., and colleagues examined data from the
National Lung Screening Trial, which compared LDCT screening vs. chest
radiography (CXR) among 53,452 people at high risk for lung cancer, to
Among 1,089 lung cancers reported in the LDCT group
during follow-up, the authors estimated that 18.5 percent represented an
overdiagnosis. They also estimated that 22.5 percent of non-small cell
lung cancer detected by LDCT represented an overdiagnosis, and that 78.9
percent of bronchioalveolar (air sacs) lung cancers detected by LDCT
represented an overdiagnosis.
“In the future, once there are better biomarkers
and imaging techniques to predict which individuals with a diagnosis of
lung cancer will have more or less aggressive disease, treatment options
can be optimized, and a mass screening program can become more
valuable,” the authors conclude.
This research was funded by grants from the
National Institutes of Health.
Lung cancer is one of the most common cancers in the world. It
is a leading cause of cancer death in men and women in the
United States. Cigarette smoking causes
most lung cancers. The more cigarettes you smoke per day and the
earlier you started smoking, the greater your risk of lung
cancer. High levels of pollution, radiation and asbestos
exposure may also increase risk.
Common symptoms of lung cancer include
cough that doesn't go away and gets worse over time
The term tomography comes from the Greek
words tomos (a cut, a slice, or a section) and graphein
(to write or record). Each picture created during a CT procedure shows
the organs, bones, and other tissues in a thin “slice” of the body. The
entire series of pictures produced in CT is like a loaf of sliced
bread—you can look at each slice individually (2-dimensional pictures),
or you can look at the whole loaf (a
3-dimensional picture). Computer programs are used to create both
types of pictures.
Most modern CT machines take continuous pictures in
a helical (or spiral) fashion rather than taking a series of pictures of
individual slices of the body, as the original CT machines did.
Helical CT has several advantages over older CT techniques: it is
faster, produces better 3-D pictures of areas inside the body, and may
detect small abnormalities better. The newest CT scanners, called
multislice CT or multidetector CT scanners, allow more slices to be
imaged in a shorter period of time.
In addition to its use in cancer, CT is widely used
to help diagnose circulatory (blood) system diseases and conditions,
such as coronary artery disease (atherosclerosis), blood vessel
aneurysms, and blood clots; spinal conditions; kidney and bladder
stones; abscesses; inflammatory diseases, such as ulcerative colitis and
sinusitis; and injuries to the head, skeletal system, and internal
organs. CT can be a life-saving tool for diagnosing illness and injury
in both children and adults.
The NCI-sponsored National Lung Screening Trial (NLST)
showed that people aged 55 to 74 years with a history of heavy smoking
are 20 percent less likely to die from lung cancer if they are screened
with low-dose helical CT than if they are screened with standard chest
x-rays. (Previous studies had shown that screening with standard chest
x-rays does not reduce the death rate from lung cancer.) The estimated
amount of radiation in a low-dose helical CT procedure is 1.5 mSv (1).
Despite the effectiveness of low-dose helical CT
for lung cancer screening in heavy smokers, the NLST identified risks as
well as benefits. For example, people screened with low-dose helical CT
had a higher overall rate of false-positive results (that is, findings
that appeared to be abnormal even though no cancer was present), a
higher rate of false-positive results that led to an
invasive procedure (such as
biopsy), and a higher rate of serious complications from an invasive
procedure than those screened with standard x-rays. NCI’s
Patient and Physician Guide: National Lung Screening Trial provides
more information on the benefits and harms.
The benefits of helical CT in screening for lung
cancer may vary, depending on how similar someone is to the people who
participated in the NLST. The benefits may also be greater for those
with a higher lung cancer risk, and the harms may be more pronounced for
those who have more medical problems (like heart or other lung disease),
which could increase problems arising from biopsies and other surgery.
People who think that they have an increased risk
of lung cancer and are interested in screening with low-dose helical CT
should discuss the appropriateness and the benefits and risks of lung
cancer screening with their doctors. They should also be aware that,
because the technique is fairly new, some insurance plans do not
currently cover it.