-- E.J. Mundell
FRIDAY, June 7 (HealthDay News) -- Researchers in South Korea
say they've developed a blood test that spots genetic changes that
signal the presence of colon cancer.
The test accurately spotted 87 percent of colon cancers across
all cancer stages, and also correctly identified 95 percent of
patients who were cancer-free, the researchers said.
Colon cancer remains the second leading cancer killer in the
United States, after lung cancer. According to the U.S. Centers for
Disease Control and Prevention, nearly 137,000 Americans were
diagnosed with the disease in 2009; 40 percent of people diagnosed
will die from the disease.
Right now, invasive colonoscopy remains the "gold standard" for
spotting cancer early, although fecal occult blood testing (using
stool samples) also is used. What's needed is a highly accurate but
noninvasive testing method, experts say.
The new blood test looks at the "methylation" of genes, a
biochemical process that is key to how genes are expressed and
function. Investigators from Genomictree Inc. and Yonsei University
College of Medicine in Seoul said they spotted a set of genes with
patterns of methylation that seems to be specific to tissues from
colon cancer tumors. Changes in one gene in particular, called
SDC2, seemed especially tied to colon cancer growth and spread.
As reported in the July issue of the
Journal of Molecular Diagnostics, the team tested the
gene-based screen in tissues taken from 133 colon cancer patients.
As expected, tissues taken from colon cancer tumors in these
patients showed the characteristic gene changes, while samples
taken from adjacent healthy tissues did not.
More important, the same genetic hallmarks of colon cancer (or
their absence) "could be measured in [blood] samples from
colorectal cancer patients and healthy individuals," the
researchers said in a journal news release.
The test was able to detect stage 1 cancer 92 percent of the
time, "indicating that SDC2 is suitable for early detection of
[colorectal cancer] where therapeutic interventions have the
greatest likelihood of curing the patient from the disease," study
lead author TaeJeong Oh said in the news release.
Oh said the test could be used either in addition to
conventional colonoscopy or perhaps as an alternative.
Experts were cautious about the potential utility of the new
"Given the overall low rate of adherence to colorectal cancer screening, having other non-invasive options to get everyone screened for colorectal cancer is never a bad thing," said Dr. Bethany Devito, a gastroenterologist at North Shore University Hospital in Manhasset, N.Y.
Devito said, however, that more research is needed before the
blood test becomes fully accepted for use. Unlike similar
gene-based tests based on stool samples, the new test "has not been
studied to prove detection of precancerous polyps," she said.
"Further studies with larger sample sizes are needed to validate
its role as an effective screening tool for the detection of not
only early colorectal cancer but also precancerous polyps."
Dr. Richard Fogler, chairman emeritus of the department of
surgery at Brookdale University Hospital and Medical Center in New
York City, said it's far too early to say that such a blood test
could eliminate the need for colonoscopy.
Even if the accuracy of the SDC2 test is confirmed in further
study, "all potential positive results will still require
colonoscopy for definitive treatment planning," he said. "Since
digital rectal exam and test for occult blood [in stool] continues
to stand the test of time for convenient, painless and inexpensive
screening, one would believe that it won't yet be replaced by SDC2,
especially depending on the cost of the test compared with how much
diagnostic value it adds."
Devito said the test might end up having a role in guiding
treatment. "Because SDC2 methylation in [blood] is frequently
detected across all colorectal cancer stages, this approach may be
useful for monitoring colorectal cancer recurrence in patients that
have already undergone treatments for their cancer," she said.
Find out more about colon cancer screening at the
U.S. National Cancer Institute.
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