Home Forums Other Specialities Gastroenterology DNA testing of stool for CRC Screening

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    Where Will Cologuard Fit Into CRC Screening?

    This week, a stool DNA test (Cologuard, Exact Sciences) was approved for colorectal cancer (CRC) screening by the US Food and Drug Administration, but where will the new test fit in? The noninvasive test joins a litany of options that clinicians can now offer individuals eligible for screening.

    Although the screening “gold standard” in the United States is colonoscopy, many adults avoid the invasive procedure. Until now, the most commonly used noninvasive alternatives have been based solely on analyses of blood in the stool. Cologuard is also based on stool DNA, and has been shown to be significantly more sensitive.

    Specifically, in its pivotal clinical trial, Cologuard was significantly more sensitive than the Fecal Immunochemical Test (FIT, Polymedco) in detecting CRCs (92% vs 74%; P = .002) and advanced precancerous lesions (adenomas and sessile serrated polyps) (42% vs 24%; P < .001). But on the downside, Cologuard was significantly worse than FIT at correctly identifying patients who were negative for CRC or advanced lesions (87% vs 95%; P < .001). The great hope for Cologuard is that it will engage patients who skip CRC screening because they want to avoid the discomfort and time required for colonoscopy. "There is potential to reach patients who have not been screened and would prefer a noninvasive option," said Daniel Chung, MD, from the Massachusetts General Hospital Cancer Center in Boston, in an email to Medscape Medical News. "The reason that gastroenterologists will like Cologuard is that it will bring more patients into screening," Kevin Conroy, chief executive officer of Exact Sciences in Madison, Wisconsin, told Medscape Medical News. Another clinician went as far as to suggest, in an editorial published this week in JAMA (2014;312:601-602), that Cologuard might someday eclipse both colonoscopy and sigmoidoscopy as the initial screening test of choice in the United States. "Stool DNA testing has the potential to reduce colorectal cancer mortality substantially while sharply reducing the number of routine colonscopies," summarized Allan Brett, MD, from University of South Carolina in Columbia. However, it remains to be seen whether there will be widespread uptake of the new stool DNA test. In fact, in their 90-site, 10,000-patient Cologuard study, Dr. Imperiale and his colleagues acknowledge that currently available data "cannot determine which test or strategy is better or preferred" (N Engl J Med. 2014;370:1287-1297). Without such data, clinicians and patients will decide for themselves how Cologuard fits their needs.

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