July 14, 2006
Blood test may find early lung cancer: study
WASHINGTON (Reuters) - A blood test that looks for the
body's own immune response to tumors may provide an easy way to
find lung cancer in patients long before an X-ray or CT scan
could, U.S. researchers reported on Friday.
The test correctly predicted non-small-cell lung cancer in
blood samples taken from patients years before they were
actually diagnosed with lung cancer, the researchers reported.
If the test's reliability can be confirmed, it might become
the first new blood screen for any cancer since the prostate
specific antigen or PSA test. The test is licensed to privately
held Rockville, Maryland-based 20/20 GeneSystems Inc.
"These data suggest antibody profiling could be a powerful
tool for early detection when incorporated into a comprehensive
screening strategy," the researchers wrote in their report,
published in the Journal of Thoracic Oncology.
Non-small-cell lung cancer is the most common type of lung
cancer, and has an average five-year survival rate of only 40
Lung cancer is by far the biggest cancer killer globally.
Each year 10 million people are diagnosed with it, according to
the Global Lung Cancer Coalition, and half of all patients die
within a year of diagnosis. It kills more than 160,000 people
annually in the United States alone.
Special X-rays known as computed tomography or CT scans can
find lung cancer tumors, but they have a high rate of false
positives -- meaning many people have to undergo a painful
biopsy to get a piece of a suspicious lump out of the lung,
only to find out it was not cancerous after all.
By the time people have symptoms of lung cancer, it is
usually too late to save them.
Li Zhong and colleagues at the University of Kentucky
developed a test that looks for certain proteins the body makes
in response to very early lung tumors.
When they tested it in people who were being treated for
lung cancer, it correctly identified 90 percent of cases, and
with very few false positives in samples taken from people who
did not have lung cancer.
They went back and tested blood samples taken from some of
the lung cancer patients years before they were diagnosed. The
test found cancer in four out of seven samples taken a year
before diagnoses, and in all 18 samples taken two, three and
four years earlier.
"Based on doubling times, a lung cancer can be present
three to five years before reaching the conventional size
limits of radiographic detection," Zhong's team wrote.