Blood Test Detects Colon Cancer
CCSA Screen Also Reveals High-Risk Growths Bound to Become Cancerous
Jan. 24, 2008 (Orlando) -- A novel blood test holds promise for both
detecting and preventing colon cancer, researchers
The test spots a protein called colon cancer-specific antigen-2
(CCSA-2) that is elevated in the presence of colon cancer or growths that are
destined to become colon cancer. In contrast, the protein appears to be rare in
low-risk colon polyps and healthy
"Right now, we really don't have a simple, accurate, and noninvasive
method for detecting colon cancer. CCSA-2 is a blood protein that predicts the
presence of the cancer with a low false-positive and false-negative rate,"
says Nicholas J. Petrelli, MD, of the Helen F. Graham Cancer Center in
"Just as importantly," Petrelli tells WebMD, the test detects
"high-risk premalignant polyps which, if left alone, will directly lead to
cancer. If we remove them, we can prevent colon cancer from
Petrelli moderated a news briefing to discuss the findings, which are being
presented at the annual Gastrointestinal Cancers Symposium (GCS) this weekend in
CCSA-2 Test Unique
Colorectal cancer is one of the most common forms of cancer, diagnosed in
more than 150,000 people each year in the United States. Although colonoscopy
can detect the disease at an early stage when it is most curable -- and even
prevent it by finding polyps before they become cancerous -- many people avoid
the procedure because of discomfort, pain, and a small risk of
There are other noninvasive tests for colorectal cancer, such as the fecal
occult blood test, which looks for blood in the stool. But occult, or hidden,
blood is also found in the stool of people with a host of other conditions,
such as hemorrhoids, resulting in
false-positive results in up to 90% of cases.
The same research team
reported earlier last year that two of CCSA-2's cousins, known as CCSA-3
and CCSA-4, can also indicate the presence of colorectal cancer.
The CCSA-2 test is unique in that it can distinguish between people who have
advanced, high-risk adenomas (growths almost certain to become colon cancers)
and non-advanced, low-risk adenomas or polyps that almost certainly will not
lead to cancer, says researcher Eddy S. Leman, PhD, an instructor in the
department of urology at Johns Hopkins Hospital in Baltimore.
"The higher the level of CCSA-2 in the blood, the greater the chance of
having colorectal cancer or a high-risk adenoma," he tells WebMD.