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Back to the Lab Articles
Saturday, 1st January 2005
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Fecal DNA analysis detected a greater proportion of important colorectal
neoplasia than fecal occult-blood testing.
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INDIANAPOLIS --A new option for non-invasive colorectal cancer
testing may encourage some people who avoid screening for the deadly
disease to be tested.
A study published in the December 23 issue of the New England
Journal of Medicine reports that a non-invasive test for DNA
mutations present in stool has an encouraging rate of detecting
colorectal cancer compared to the standard non-invasive method --
fecal occult (hidden) blood stool testing, although neither
approached the detection rate of colonoscopy, an invasive procedure.
"A simple, non-invasive test that detects tumor-specific products
with reasonable sensitivity and specificity might overcome barriers
to screening among persons who are not willing to have a more
invasive test, such as colonoscopy," said Thomas Imperiale, M.D.,
professor of medicine at the Indiana University School of Medicine
and a research scientist at the Regenstrief Institute.
The study, conducted at 81 sites by Dr. Imperiale and colleagues
of the Colorectal Cancer Study Group, reports that in average risk,
asymptomatic individuals the fecal occult blood test -- which tests
blood hidden in stool -- found only 13 percent of colorectal cancer;
while the new stool DNA test detected 52 percent of the cancers.
Colonoscopy, which is presumed to find all colon cancers, is the
"gold standard" against which all other tests are measured.
Typically, colorectal cancer develops slowly over a period of
several years, usually beginning as a growth of tissue known as a
polyp that develops on the lining of the colon or rectum. Most
cancerous lesions bleed intermittently, however many precancerous
polyps do not bleed. Absence of fecal occult blood cannot rule out
cancer or precancerous lesions.
Previous studies have found that polyps as well as cancerous
lesions may shed abnormal DNA. It is this DNA which the stool DNA
panel analyzes. Although researchers found that the majority of
precancerous polyps discovered during colonoscopy were not detected
by either non-invasive test, they report that the stool DNA panel
detected a greater proportion than did analysis of stool blood.
Despite national guidelines recommending screening, fewer than
half of American adults aged 50 years and older have had a recent
examination for colorectal cancer at the proper interval according
to Centers for Disease Control.
"There are many reasons why people don't get screened for colon
cancer," said Dr. Imperiale. "Some individuals do not want
colonoscopy because of discomfort despite conscious sedation, its
inconvenience, or its risk for complications; others are unwilling
to smear stool samples on a card for the occult blood test every
year." The stool DNA panel test, which requires a single sample
expelled from the body directly into a container, gives people who
are not getting screened with any of the currently available
methods, another noninvasive option.
According to the American Cancer Society colon cancer is the
third leading cause of cancer death among men and women in the
United States.
References:
N Engl J Med. 2004;351:2704-2714,
2755-2758.
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