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Spiral CT Scanning Finds Very Early Lung Cancers

Spiral CT Scanning Finds Very Early Lung Cancers

WASHINGTON—The Early Lung Cancer Action Program (ELCAP) has tested CT
screening over the last decade and shown significant improvements in screening
technology and substantially improved cure rates for cancers caught early.

At the lung cancer workshop Application of High Resolution CT Imaging Data
to Lung Cancer Drug Development, sponsored by the Cancer Research and
Prevention Foundation, Claudia I. Henschke, MD, PhD, presented the most recent
results from ELCAP. She also provided a glimpse of imaging’s future, in which a
CT image could give as much detail as a pathology image.

Every time a cell divides it’s called a doubling, said Dr. Henschke,
professor of radiology, Weill Medical College of Cornell University. It takes
about 40 doublings for lung cancer to reach the size that causes death from
primary disease or metastasis, she said. A chest x-ray can reveal, at best, a
1-cm cancer, but typically only detects cancers that are 2 cm or larger. These
are cancers that have already undergone about 30 to 32 doubling times. Helical
or spiral CT, on the other hand, can detect 2-mm lesions. These lesions have
undergone about 22 doubling times, which is still in the second half of the
lifetime of the lung cancer, Dr. Henschke said. "The exciting potential of
newer CT technologies that we’re working on is that we can finally get into the
first half of the lifetime of that lung cancer and detect lesions that are 1 mm
or smaller," she said.

ELCAP started in 1993 screening individuals at high risk for lung cancer—age
60 and older with a smoking history of a pack-a-day for 10 years. The
international collaboration, involving 33 institutions, has accumulated 26,557
baseline scans, 19,742 repeat scans, and 373 cancers. They are collaborating
with several European screening trials using the same system to pool data.

Of cancers detected to date in ELCAP, 80% were stage I disease, a stark
contrast to usual care, in which only 5% to 15% of lung cancers are diagnosed
at stage I. The 8-year case fatality rate for all stages of resected patients
in ELCAP was 4%. In the National Cancer Institute’s Surveillance, Epidemiology,
and End Results (SEER) program, overall fatality is about 30%.

Throughout the past decade, Dr. Henschke’s team has been applying
technological improvements to ELCAP. The latest advance is volume CT, which was
developed based on research from Dr. Henschke’s group. In helical or spiral CT,
the table moves around the patient as each row of detectors scans a part of the
body. One row of detectors was improved to 2 rows, and soon to 64. The image is
then built from 64 slices. With volume CT, instead of rows of detectors, one to
four plates are in the scanner, allowing continuous slicing. "These plates are
getting all of the information at one time, instead of one row at a time," she
said. It increases resolution, and the patient is in the scanner for a very
short time.

New scanners—used only in mice, but to be tested soon in humans—can obtain
the whole volume of the lungs and improve resolution 30-fold over today’s best
scanners, she said. The scans show bronchi, bony skeleton, and sternum. "It
will make a big difference in what we can see," she said. Along with better
imaging devices have come improved image processing, which will "provide more
analytic tools to identify and measure abnormal areas ," Dr. Henschke said.

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