OncoLog, Volume 56, Number 7, July 2011 Page: 6
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Landmark Trial Shows Potential of Low-Dose
Computed Tomography for Lung Cancer Screening
[Continued from page 5]but that's not the kind of person we
screened in the trial."
Most researchers, Dr. Munden said,
agree that individuals at high risk are
those who have had heavy exposure to
smoking and have lived long enough to
develop lung cancer. Many researchers
believe such a person is one who has a
smoking history of 20 or more pack-
years and is at least 50 years of age.
"Part of the issue is who not to
screen as much as it is who to screen,"
Dr. Munden said. "What we do not
want to do is screen a 40-year-old
woman who has a casual or minimal
smoking history, because the benefit
does not justify the risk."
Chief among the screening proce-
dure's risks is ionizing radiation expo-
sure, which can increase a patient's life-
time risk of developing cancer. (The
risk is higher in women because breast
tissue, which is highly radiosensitive,
also receives the most radiation from
chest CT.) In the United States, the
average annual exposure to ionizing
radiation is about 3.1 mSv-half from
natural sources and half from manmade
sources, mostly diagnostic medical pro-
cedures. Diagnostic CT delivers up to
8 mSv. Low-dose CT, which was used
in the NLST, delivers about 1.5 mSv.
By comparison, a series of conventional
chest radiographs delivers about 0.06
mSv. In older patients with a long his-
tory of smoking-such as those includ-
ed in the NLST-the benefit of identi-
fying a cancer at a treatable stage is
more likely to outweigh the risk a small
dose of ionizing radiation conveys.
In the absence of established screen-
ing guidelines, Dr. Munden said, physi-
cians should rely on their experience
and judgment in determining which
patients are at high risk. "If you think a
patient of yours has a significant risk of
lung cancer based on some criteria that
you're comfortable with, I encourage
you to get the patient screened," he said.
Biomarker studies
In addition to undergoing CT or
chest radiography, more than 10,000trial participants-including those
enrolled at MD Anderson-submitted
sputum, blood, and urine specimens as
part of the NLST's biomarker study.
The goal of the biomarker study is to
identify genetic differences between
trial participants who developed lung
cancer and trial participants who did
not develop lung cancer. Although it
is not yet under way, according to Dr.
Munden, the biomarker study is inte-
gral to identifying the best candidates
for lung cancer screening.
"To me, this will be the most impor-
tant part of the trial," Dr. Munden said.
"If you think about who should be
screened for lung cancer, the answer's
probably in a blood test that tells us
this person has the genetic predisposi-
tion to develop lung cancer. That's
the person we'll screen." However,
Dr. Munden added, "We're not any-
where close to being there."
Lung cancer screening
at MD Anderson
Dr. Munden and other faculty
members-including Therese Bevers,
M.D., a professor in the Department of
Clinical Cancer Prevention; Stephen
Swisher, M.D., chair of and a professor
in the Department of Thoracic and
Cardiovascular Surgery; and George
Eapen, M.D., an associate professor
in the Department of Pulmonary
Medicine-are in the initial phases
of establishing a lung cancer screening
program at MD Anderson.
"We're not just going to screen peo-
ple," Dr. Munden said. "We want to
collect data that can help answer some
questions down the road, so the program
will have a clinical research component
as well." He added that a smoking cessa-
tion program is offered as an integral
part of the screening program.
The group has initiated the screen-
ing program at MD Anderson's main
campus in the Texas Medical Center
and plans to eventually implement the
program at the institution's regional
care centers. People aged 50 years and
older with a smoking history of at least20 pack-years are eligible. A physician
referral is not required, Dr. Munden
said, but patients must have a doctor
who can be contacted in the event
something is found. Physicians are
encouraged to refer patients they
believe to be at a high risk of develop-
ing lung cancer.
More questions
Dr. Munden said that the initial
results of the NLST are expected to
be published this summer. In the mean-
time-and for some time hereafter
NLST researchers will continue to
grapple with the multitude of questions
raised by the trial's findings.
"The bigger questions now are, who
do we screen and when do we screen
them? And how often do we screen
them?" Dr. Munden said. "As we dis-
cover answers to these and other ques-
tions, lung cancer screening programs
will help us improve people's health
and save lives."
FOR MORE INFORMATION
Dr. Reginald Munden ...........713-792-3492
ADDITIONAL RESOURCES
MD Anderson Lung Cancer
Screening Program. http://www.
mdanderson.org/patient-and-cancer-
information/cancer-information/
cancer-topics/prevention-and-
screening/cancer-screening-
guidelines/lung-cancer-screening.htmI
National Lung Screening Trial
Research Team. The National Lung
Screening Trial: overview and study
design. Radiology
2011;258:243-253.
National Cancer Institute. National
Lung Screening Trial: Questions and
Answers. Updated November 26,
2010. http://www.cancer.gov/
newscenter/qa/2002/nlstqaQA.6 OncoLog July 2011
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University of Texas M.D. Anderson Cancer Center. OncoLog, Volume 56, Number 7, July 2011, periodical, July 2011; Houston, Texas. (https://texashistory.unt.edu/ark:/67531/metapth639573/m1/6/: accessed July 17, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting UNT Libraries Government Documents Department.