Cologuard: Breakthrough in CRC Screening

John L. Marshall, MD


September 05, 2014

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Good morning, everyone. It is a beautiful first day of school here in Washington, DC. Hope your kids have gone off. I am now an empty-nester; my youngest has just gone off to college. I am not sure what we are going to do -- perhaps more videos for Medscape, for goodness' sake, with all my free time.

Today I want to talk about a new technology that was just approved for colon cancer screening. This is Cologuard®, a long-awaited test of stool DNA changes for early detection of colon cancer.

You know the story. We have been terrible about screening for colorectal cancer. We have just not done a good job. You are supposed to begin screening at age 50 -- age 45 for African Americans. We are supposed to do this regularly, and yet, we have a very poor uptake among the US population.

What really irks me is that we know that genetically there are 2 basic kinds of colon cancer. One type occurs with an early polyp and one occurs without. Thus, the screening techniques we use today really only target that patient with the early polyp for whom we perform colonoscopies at intervals, every now and then.

The rest of the world does not use colonoscopy for screening. They do fecal occult blood testing, sometimes sigmoidoscopy. So, there is a great deal of debate out there.

Stool DNA Testing Performs Well

This new test is a stool DNA test. It performed better than the FIT (fecal immunochemical test) in terms of detection but was slightly less accurate. This means that we will see a few more false positives with this test, but nonetheless it is a useful test. It will be more expensive; we are looking for DNA changes, methylation changes, and fecal blood, all in one test, but it did perform a bit better than FIT.

I believe the role -- the niche -- for this technology will be in that group of patients who refuse colonoscopy or cannot have colonoscopy. There probably will be some crossover with colonoscopy, and this test will be used along with that. Regardless, whatever it takes to get people to undergo screening to keep them out of my office is valuable.

Look out for this new test. I think it will be useful. It will be covered by insurance. Probably we need to rethink when we begin to screen folks -- maybe even earlier than age 50, given the shift in age of early colon cancer.[1] But let us get our patients screened, talk about this with them, persuade them to do one test or another. I do not care how, but get them screened. Keep them out of my office.

This is John Marshall for Medscape.


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