Can Stool Tests Really Detect Colon Cancer?

The Short Answer from a colorectal surgeon

Q: Can stool tests detect colon cancer?

A: Two types of home stool tests are promoted as easy, noninvasive screening tools for colorectal cancerScreening is vital because symptoms do not appear in this cancer’s early, more treatable stages.

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The older hemoccult test finds hidden blood in the stool. Its accuracy in detecting cancer varies but can be as high as 70 percent. However, the hemoccult test cannot detect colorectal polyps.

Finding these polyps is vital because, while only about one in 200 polyps ever turns into a cancer, all colorectal cancers come from a precancerous polyp or lesion.

A newer home test looks at DNA in the stool for evidence of colorectal cancer. It detects about 92 percent of the cancers that are present and also finds approximately 40 percent percent of precancerous polyps.

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However, if either the stool DNA test or the hemoccult test is positive, you will still need a colonoscopy to find and remove the precancerous or cancerous lesion.

Colonoscopy remains the gold standard for cancer screening because — in one single test — we can detect the vast majority of polyps, remove them and prevent cancer.

That said, if you can’t get a good colonoscopy or if colonoscopy is not covered by insurance, a stool DNA test is a reasonable alternative.

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—Colorectal surgeon James Church, MD

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