Not such a pain in the rear

Posted by Richard Linney on Feb 01, 2002 at 04:47 (

The lowly stool sample may be far more valuable than most people think. By painstakingly sifting through the genetic contents of stool samples, researchers have devised a screening test that can detect colon and rectal cancers in their earliest, most curable stages.
Although colorectal cancer is highly curable when caught early enough, it remains the second leading cause of cancer deaths in the United States. That's because many people don't seek preventive screening. The most effective detection tool is a colonoscopy, which requires doctors to snake a 2-meter-long endoscope into the large intestine (ever so gently around the curves, please) to look for abnormalities and tumors. Aside from being distinctly uncomfortable, colonoscopies are also expensive. A simpler screening method, analyzing stool samples for traces of blood (one symptom of colorectal cancer), is rarely conclusive.

The new technique involves screening stool samples for a gene called APC . Mutations of APC can trigger the growth of tumors, and mutated APC is found in nearly all malignant colorectal tumors. Now, oncologists Bert Vogelstein and Kenneth Kinzler and their team at the Kimmel Cancer Center at Johns Hopkins University in Baltimore have shown that mutant APC DNA can be detected in cells sloughed from the intestinal lining into the feces. The team used PCR--the standard method for replicating DNA--to amplify the APC DNA in stool samples from 74 patients. Samples containing mutated APC genes produced dysfunctional proteins, allowing them to be easily identified.

The technique accurately detected mutated APC DNA in 61% of the patients already diagnosed with early-stage premalignant colon cancer and identified mutations in 50% of patients known to have benign tumors, the team reports in the 31 January issue of The New England Journal of Medicine. The test produced no false positives for a cancer-free group.

"This work definitely needs to be pursued," says Barbara Conley, an oncologist at the National Cancer Institute in Bethesda, Maryland. Although Conley points out that more work needs to be done to improve the sensitivity of the test, she says it could one day provide a welcome alternative to colonoscopy.

Article found at ScienceNOW

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