NEW YORKA program to screen for lung cancer that was
remarkably successful in recruiting participants has produced some surprises
and taught the investigators some lessons about what to expect from large-scale
lung cancer screening.
James R. Jett, MD, consultant in pulmonary and critical care
medicine and medical oncology, Mayo Clinic, reported the findings at the 3rd
International Conference on Screening for Lung Cancer.
The Mayo Clinic study, launched in January 1999, enrolled 1,520
individuals within 12 months, when recruitment stopped. "We have a waiting
list of 3,000 individuals who did not get into the trial," he said.
Eligibility requirements included being age 50 or older, a
history of at least 20 pack-years of smoking, and a 5-year life expectancy. The
mean pack-years for the enrolled group was 45, with 61% of the participants
being active smokers and 39% having stopped smoking. Men made up 52% of the
group, women 48%.
Screening includes sputum cytology and spiral CT scanning with
low-dose radiation. The GE scanner used, Dr. Jett said, has 5 mm collimation
and 3.5 mm reconstruction intervals. Because scanning from the top of the lungs
to the iliac crest can be done in 12 seconds, patients are in and out of the
scanner in less than 5 minutes, he said.
Scans are repeated annually for 3 years, and most patients have
now had their first repeat scan.
The first surprise the researchers encountered was that the
initial scan produced many more positive scans than expected. "We detected
a nodule in 51% of our individuals with the thin-section CT scans, a total of
1,300 nodules," Dr. Jett said.
About 90% of the nodules were 7 mm or less in diameter.
"So far, we’ve found no cancers in nodules 7 mm in size or less,"
he said. "It will happen, but we haven’t found them yet." Nodules
were 8 mm or larger in 11% of participants.
To date, Dr. Jett said, with second-year scans completed in
about 75% of participants, "we have detected 19 prevalence cancers [ie,
initial scan positive] and 2 incidence cancers [ie, year-2 scan
Of the 18 non-small-cell lung cancers detected, 88% were stage
I and II. Seventeen were detected on initial screening and one, a stage IIA
squamous-cell carcinoma, was found on second-year screening. Of the three
small-cell lung cancers detected, two were found in the prevalence scan and one
in the incidence scan.
"With aggressive, fast-growing cancers, it’s
questionable how good screening is going to be, Dr. Jett commented. "We
are not going to cure small-cell lung cancers found with a screening
scan," he said.
Analysis of the repeat scans of 1,026 persons has been
completed, Dr. Jett said. With just a year between scans, he noted, "20%
of the time, in retrospect, we saw a nodule that we had missed the year
before." These nodules ranged from 1 mm to 20 mm in size. "Most of
them were small," he said, "but some of them are larger. This is a
New nodules were detected in 12% of the individuals who have
had repeat scans. "You’d better have a database where you can analyze
all of this," Dr. Jett cautioned, "and you’d better have good
comparisons with the previous CT scans. Next year, it’s going to be even
tougher, because we’re going to have to compare the CT scans with two prior
In addition to finding lung cancers, the scans at the Mayo
Clinic have also detected three kidney cancers, 50 abdominal aortic aneurysms,
an atrial myxoma, a bronchial carcinoid tumor, and a breast cancer. "This
is what you’re going to find," Dr. Jett said, "and you’d better
be prepared to be sending letters out to these people as to what they need to
do in their follow-up."