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Noninvasive Screening Tool for Colorectal Cancer

DNA analysis out-performs fecal immunohistochemical test

The results of a clinical trial of Cologuard (Mayo Clinic/Exact Sciences) have shown unprecedented rates of precancer and cancer detection by a noninvasive test. The detection rates are similar to those reported for colonoscopy.

The new findings were published in the March 20 issue of the New England Journal of Medicine.

“Polyps and cancer, both lesions, continuously shed cells that end up in the stool. The Cologuard test can recover cancer- or polyp-related DNA in those exfoliated cells and determine whether there’s the presence or absence of the right signature of a target lesion,” said study author David Ahlquist, MD, co-inventor of the Cologuard test.

Cologuard is a noninvasive DNA test for the early detection of colorectal precancer and cancer. The test uses a stool sample that is analyzed for DNA signatures of precancer or cancer. The samples are easily collected and mailed from home, and require no bowel preparation, medication restrictions, or changes in diet.

The DeeP-C trial included 10,000 patients and was designed to determine how well the Cologuard test detects precancer and cancer. The study also compared Cologuard with the fecal immunochemical test (FIT) for occult blood. The study was conducted at 90 medical centers in the U.S. and Canada.

All of the patients received Cologuard, FIT, and colonoscopy. Colonoscopy was the reference method. Major findings included the following:

  • The overall sensitivity of Cologuard for cancer was 92%, and the test showed 94% sensitivity for the earliest and most curable cancer stages (stages I and II).
  • The test’s sensitivity was 69% for precancerous polyps at greatest risk to progress to cancer (i.e., those containing high-grade dysplasia).
  • Cologuard detected significantly more cancers and significantly more precancerous polyps compared with FIT.

Colorectal cancer is often considered the most preventable, yet least prevented, cancer. Nearly 50% of adults aged 50 years and older have not been screened as recommended, and, as a result, colorectal cancer has become the second-leading cause of cancer death in the U.S. Colorectal cancer is highly treatable if found early, and it is preventable if the precancerous polyps at greatest risk of progression can be detected.

Cologuard works by testing a patient’s stool for altered DNA shed during digestion. Altered DNA is known to occur within colorectal cancers and precancerous polyps. The test also examines the stool for the presence of blood — another possible indicator of colorectal cancer. Combining the data from the stool DNA test and the blood test into a single result provides a comprehensive screening approach.

Exact Sciences, the co-developer of Cologuard, is in the process of seeking approval from the FDA for use of the test for colorectal cancer screening. The company is scheduled to appear before the Molecular and Clinical Genetics Panel of the agency's Medical Devices Advisory Committee on March 27.

Sources: ; March 20, 2014; and Medical Xpress; March 19, 2014.

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