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Cancer Imaging
A visual introduction to cancer imaging, featuring information about imaging technologies and their uses, imaging trials, and recent imaging developments.
Understanding Screening Trials
Screening trials are clinical trials which test new ways of finding cancer in people before they have any cancer symptoms.
Lung Cancer Home Page
NCI's gateway for information about lung cancer.
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The National Cancer Institute (NCI) is recruiting 3,000 current and former
smokers for the Lung Screening Study, a year-long, $3 million study of spiral
computed tomography (CT) scans, promising but unproven technology for lung
cancer screening. While the study will not determine if the scans save lives --
the gold standard for any cancer screening test -- it will gauge the
feasibility of a larger, longer study designed for that goal.
Spiral CT uses X-rays to scan the entire chest in about 15 seconds, during a
single breath-hold. Throughout the procedure, the patient lies still on a
table. The table and patient pass through the CT machine, which is shaped like
a donut with a large hole. The machine rotates around the patient and a
computer creates images from the scan, assembling them into a 3-D model of the
lungs. The amount of radiation absorbed during a spiral CT scan is comparable
to that absorbed during a mammography.
During September and October 2000, six screening centers across the country will
each recruit 500 people and randomly assign them to receive either a spiral CT
scan or a chest X-ray. First, researchers will determine the willingness of
smokers and former smokers to participate in a randomized study. In addition,
they will compare the lung cancer detection rate of each test; measure how much
and what kind of medical follow-up is needed for positive or ambiguous results;
and track how frequently participants receive spiral CT scans outside of the
study.
All of this knowledge is crucial for the design of larger, more definitive
studies, said John Gohagan, Ph.D., the NCI investigator heading the study. "In
a relatively quick time frame we will learn if smokers are willing to be
randomized to receive something other than a spiral CT scan. We will also learn
about the medical follow-up of people who have the scans, how extensive and
expensive it tends to be," he said. Gohagan is chief of the Early Detection
Research Group in NCI's Division of Cancer Prevention.
Board certified radiologists will review each CT scan and X-ray; results will be
mailed to participants and their physicians within three weeks of the screen.
For those with positive chest X-rays, the screening center will recommend
standard follow-up care. Because no such standard of care exists for spiral CT
scans, participants with suspicious scans will be referred to their primary
care physician and advised to consult a specialist for follow-up.
Evidence from early studies suggests that spiral CT scans detect small lung
cancers, often at the edges of the lungs. However, whether finding these tumors
actually saves lives remains unknown. The only way to detect a survival
advantage is with a large study where people receiving the scans are tracked
alongside a control group that does not get them; such research would be
expensive, requiring tens of thousands of participants and five or more years.
Thorough review of results from the Lung Screening Study will help researchers
decide whether such a study is feasible.
Some in the medical community question whether smokers will participate in a
clinical trial in which they might be randomized to receive a screening exam
other than spiral CT. Screening spiral CT scans are available outside of
clinical trials, though they cost $300 to $1,000 and health plans generally do
not cover the charges. About half of the hospitals in the United States own
spiral CT machines, each costing upwards of $1 million. Some of these hospitals
have begun aggressively advertising the scans for the early detection of lung
cancer, despite the lack of evidence that the scans reduce a person's
likelihood of dying from lung cancer.
Furthermore, no estimates exist on the cost -- in terms of dollar amounts or
risk to the patient -- of the follow-up care that screening with CT scans may
require. Scarring from smoking and other noncancerous changes inside the lungs
tend to mimic tumors on the scans, challenging the radiologists who read them.
Interpretations of the scans often vary, leading to disagreement about
follow-up care. Radiologists and clinicians often recommend additional scans,
biopsies, chest surgery, or other diagnostic tests.
In fact, a
recent report (a 20-year follow-up of the
Mayo Lung Project, which used chest X-rays to screen for lung cancer,
published in the Aug. 16, 2000, Journal of the National Cancer Institute)
suggests that screening for lung cancer may detect tumors that never become
life threatening. Called over-diagnosis, this phenomenon may put screening
recipients at risk from unnecessary biopsies or surgery. Possible complications
from these procedures include chronic pain or nerve damage. By following
participants after spiral CT scanning, the Lung Screening Study will help
researchers understand risks associated with the scans.
For quick results, the study builds on the scientific infrastructure of the
150,000 participant Prostate, Lung, Colon, and Ovarian Cancer Screening Trial (PLCO),
launched by NCI in 1992. As all are involved in PLCO, the six Lung Screening
Study centers offer extensive experience recruiting and tracking participants
in cancer screening studies.
The six participating centers are Georgetown University Medical Center/Lombardi
Cancer Research Center (Washington, D.C.); Henry Ford Health System (Detroit);
the University of Minnesota School of Public Health/Virginia L. Piper Cancer
Institute (Minneapolis); Washington University School of Medicine (St. Louis);
Marshfield Medical Research and Education Foundation (Marshfield, Wis.); and
the University of Alabama at Birmingham. In addition, Westat, Rockville, Md.,
will serve as the data coordinating center.
Lung cancer is the leading cause of cancer-related death in the United States,
expected to claim 156,900 lives this year. It will be diagnosed in an estimated
164,100 people in 2000, usually only after symptoms appear. To date, no
screening technology has been proven effective in reducing the number of deaths
from lung cancer. Approximately 85 percent of lung cancers are caused by
smoking.
To be eligible for the study, participants must be between the ages of 55 and
74. Participants also must have a history of long-term or heavy smoking; former
smokers must have quit within the last 10 years. People who have a history of
lung cancer or who are participating in PLCO are ineligible.
Call the NCI's Cancer Information Service at 1-800-4-CANCER for more information
about the Lung Screening Study or for information about quitting smoking or
lung cancer.
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