A scoop of poop may save your life

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Which of the following activities makes you more squeamish: (a) undergoing a colonoscopy, or (b) scooping up samples of your own poop?

A team of researchers from Japan and Baylor University Medical Center in Dallas is betting that the answer is (a). And so they have developed a test to diagnose gastrointestinal cancers by analyzing the DNA fragments in human feces.

The test relies on the fact that cancerous growths in the GI tract produce longer strands of DNA, and that those strands are more likely than other pieces of DNA to be sloughed out of the body via feces.

The researchers identified two genetic biomarkers that were correlated with the severity of colorectal and gastric cancers. Then they tested 303 stool samples from volunteers who were suspected of having colorectal tumors.

This was a hands-on project. According to a study published today in the Journal of the National Cancer Institute, “Patients were instructed to collect an aliquot of feces using a paper spoon and to store it in a hermetically sealed plastic container.” The container was then sealed in a Ziploc bag and stored overnight in the volunteer’s refrigerator or freezer, then brought to a hospital the next day.

The researchers were able to isolate the key fragments of DNA and use them to diagnose cancers. But the test wasn’t perfect. When they ran the test on stool samples from 43 volunteers, one of the markers led to a false positive and seven false negatives; with another marker there were two false positives and nine false negatives. Markers from another gene had no false positives but several false negatives. The study’s authors acknowledge the test would be better with more reliable biomarkers.

In an editorial accompanying the study, gastroenterologist Steven Itzkowitz of the Mount Sinai School of Medicine in New York wrote that colorectal cancer can be easily prevented through routine screening, but the discomforting prospect of a colonoscopy – together with the cleansing bowel prep that precedes it – means that many patients skip this accurate and life-saving test. In this context, a noninvasive stool screening test would be valuable. He added that the same approach could potentially be used to diagnose cancers of the oropharynx, esophagus, pancreas, bile duct and gall bladder.

-- Karen Kaplan