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It’s been difficult for TV watchers to avoid the sprightly Cologuard box jumping around on its spindly blue legs, beckoning viewers to take an at-home, stool-based test for colorectal cancer. Joining in the multimillion-dollar national public relations and advertising blitz by Cologuard’s maker, Exact Sciences, are singer/actor Harry Connick Jr., golfer Jerry Kelly, and the Green Bay Packers.

Celebrity endorsements of health care products are nothing new. As early as 1958, Milton Berle’s jokes about Miltown, an antidepressant, were promoted to gossip columnists by the drug’s maker. Today’s direct-to-consumer marketing makes Berle’s efforts seem tame in comparison. Many such campaigns, including the one for Cologuard, seem like public health campaigns that are barely recognizable for what they really are: product advertisements.

The increased attention to Cologuard has resulted in more than 1.3 million people using the test. And with the recent announcement of a marketing partnership with Pfizer that will increase the size of the sales force promoting Cologuard to primary care physicians and hospitals, this may be just the beginning.


Make no mistake: Increased screening for colorectal cancer is important. It’s the third most common type of cancer (excluding skin cancer) in the United States, and is expected to kill more than 50,000 Americans this year.

But many gastroenterologists like me are concerned about the referral cases we’re seeing for follow-up colonoscopies triggered by positive Cologuard tests, especially those in which Cologuard should not have been prescribed in the first place. Many of us are also concerned that an outsized focus on convenience is overshadowing serious limitations of the test.


For me, it’s personal. I will never forget trying to find the right words to comfort my uncle who was dying from colon cancer — a disease I have spent my professional life trying to prevent.

There are four main ways to screen for colorectal cancer. (Screening means trying to find hidden cancer in seemingly healthy people.) Colonoscopy is the gold standard. It uses a flexible, lighted tool called a colonoscope to view the entire colon and remove cancerous and precancerous growths called polyps if they are detected. CT colonography uses a CT scanner and computer programs to create a three-dimensional view of the inside of the colon and rectum that can be used to identify polyps or cancer. Another method is the fecal immunochemical test (FIT), which checks stool for tiny amounts of blood given off by polyps or colorectal cancer. Cologuard tests stool for tiny amounts of blood as well as for certain abnormal sections of DNA in cells shed by cancer or polyps that end up in the stool.

In 2014, researchers funded by Cologuard’s maker published in the New England Journal of Medicine results of a study of 10,000 patients comparing three methods of colorectal cancer screening. Screening colonoscopy was better at finding cancer and pre-cancerous polyps than both Cologuard and the FIT test. Cologuard found 93 percent of the cancers detected by screening colonoscopy. That’s a great result, but when we’re talking about cancer, missing 7 percent is a big deal. That means Cologuard could fail to detect colorectal cancer in 1 out of every 13 people who use the test — a significant number considering that more than a million people have used it and many more will likely use it.

Ninety-five percent of colon cancers begin as polyps. Cologuard is not as good at finding pre-cancerous polyps and, unlike colonoscopy, it can’t remove them. According to the NEJM study, Cologuard misses more than 30 percent of polyps that will soon be cancer, and 57 percent of polyps that may become cancer.

I got deeply concerned about this when I read news reports that Exact Sciences stock jumped double digits in May 2018 because new screening guidelines from the American Cancer Society potentially increased the market for Cologuard by 20 million Americans when it lowered the minimum age for colorectal screening from age 50 to age 45.

Don’t get me wrong. Cologuard is a good screening test. In fact, I was one of the physicians who provided patient data for its initial validation study. The Multi-Society Task Force on Colorectal Cancer recommends Cologuard as an acceptable second-line screening option. The task force concluded that physicians should recommend colonoscopy first. For patients who decline to have one, the FIT test should be offered next, followed by second-tier tests such as Cologuard and CT colonography for patients who decline both of the first-line options.

Some people should not be prescribed Cologuard at all. It is not approved for individuals at high risk of colorectal cancer, including those with conditions that increase the risk, such as a personal history of polyps, inflammatory bowel disease, chronic ulcerative colitis, Crohn’s disease, or familial adenomatous polyposis; or a family history of colorectal cancer or polyps.

The task force ranked colonoscopy in the top tier of screening tests because it is the only test that not only detects colorectal cancer but also prevents it by removing polyps during the procedure. It is the only test that is appropriate for people who have risk factors such as a personal or family history of colorectal cancer or polyps.

Almost 1 in 6 people who use the Cologuard test will have a positive result that suggests the presence of colorectal cancer. They will no doubt worry they have colon cancer while scheduling and preparing for the recommended follow-up colonoscopy. For almost half of them (45 percent), the colonoscopy will show they do not have cancer.

Individuals with a positive Cologuard test who are covered by Medicare may face a costly bill because insurance covers 100 percent of the cost of colonoscopy as a preventive screening test, but a follow-up colonoscopy for a positive Cologuard is considered a diagnostic or therapeutic service and may not be fully covered.

Colorectal cancer is the second leading cause of cancer death in the United States, behind lung cancer, but the survival rate is very high if it is found early. Preventing cancer is even better than finding it early. If our goal is to prevent colorectal cancer, then finding, quantifying, localizing, and removing polyps is the most effective strategy.

Every time I diagnose colorectal cancer, I feel like the system has failed.

Some day we may have a simple blood, saliva, or stool test that can detect colorectal cancer and polyps better than colonoscopy. There may even be medications to remove the cancer or dissolve polyps. When that day arrives, I will prescribe that new screening test because the science is sound and it is in the best interest of my patients. Until then, I will counsel physicians and their patients to choose science over convenience. That choice should be screening colonoscopy, the only test that can both detect and prevent colorectal cancer.

Naresh Gunaratnam, M.D., is a gastroenterologist and research director at Huron Gastroenterology in Ypsilanti, Michigan; chief medical officer of Lean Medical Technologies; and a speaker for Medtronic about esophageal cancer.

  • I am a 74 year old male with two negative colonoscopies and no family history of colon cancer. I was notified last month that 10 years had elapsed and it was time to do it again. The problem was that, since my last colonoscopy, I have been put on Coumadin blood thinner for atrial fibrillation. In order to have the colonoscopy, I would have to replace the Coumadin from five days prior to the procedure to several days after it (when my Coumadin numbers got back into range). During this interval I would have to use a different blood thinner, Lovenox, which clears the system much more quickly. Lovenox, however, must be injected twice daily into the abdominal fat. I did that when I had a hip replacement, and vowed never to do it again unless absolutely necessary .

    So my primary care doc prescribed Cologuard, the test went nicely, and I got a negative result. Can I live with a 7 in 100 chance that the Cologuard missed something that would have been found by the colonoscopy? You bet I can!!

  • You said: Cologuard found 93 percent of the cancers detected by screening colonoscopy. That’s a great result, but when we’re talking about cancer, missing 7 percent is a big deal. That means Cologuard could fail to detect colorectal cancer in 1 out of every 13 people who use the test — a significant number considering that more than a million people have used it and many more will likely use it.

    I also think your math is way off, unless you’re assuming that 100% of the people using the Cologuard test have cancer. No, it fails to detect cancer in 7% of the people who HAVE cancer. If it detected cancer in 9,300 people, that’s a potential of 700 people it missed (NOT, as you say, 1 in 13 of the whole million and a half). 700 as a percentage of 1,500,000 is, surely, WELL within any acceptable margins of error.

  • We can be thankful to live in an era of such technology as DNA and to be able to be screened via a noninvasive test such as Cologuard. Medicare covers fully the cost of Cologuard and today over 95% of patients are covered with no out of pocket costs and are spared the many hassles and risks of a colonoscopy. Cologuard was given a “A” rating by the USPSTF and was unanimously passed by the FDA in 2014 with at least one member saying it’s the biggest breakthrough in screening in 25 years.

    Cologuard detects early stage cancers just as accurately as colonoscopy for a lot less money.

    Colonoscopy misses as much as 11% of cancers aand is likely a death sentence due to the 10 year screening interval. A false positive (less than 9% for patients 65 and under) results in a very thorough colonoscopy.

    Make your screening choice wisely.

  • I wish I had found this article 2 weeks ago. At my annual physical my doctor told me about the Cologuard and determined I was not at high risk. She suggested I do that.
    I already had a endoscopy scheduled for Barrett’s esophogus and was due for the colonoscopy after 10 years.
    So I went ahead with the Cologuard but don’t have the results yet. Now I am thinking I want the colonoscopy but am not sure if Medicare will pay for it since they paid for the Cologuard. I am angry that I jumped so fast to take the less invasive especially since I will already be having sedation for the endoscopy.

  • Naresh, I think your math may be wrong. OK, if 1 in 6 people test positive with Cologaurd, that is about 16%. But we know that 16% of people between 50 and 70 years old are not afflicted. OK, so now these 16% (about 16 of 100 people) get a colonoscopy and you say about half of them are afflicted. That would mean there are now 8 people per 100 of the general population that are afflicted. I may be wrong, but that sounds very high.

  • Dear Naresh Gunaratnam,
    Thank you for the article and your sincerity in your profession with the concern for your patients. I personally don’t feel that ‘the system has failed’ you or science but perhaps the underlying cause of cancer itself. I’m so distraught that science itself has proven that there are known carcinogens and toxins that are in our food supply and many of our natural resources, of which a few cannot be avoided, they are repeatedly permitted by the regulators. We are told that these that are detected are okay because they are below the permitted percentage. My question would then be do these have an accumulative effect on our system or how do our bodies respond to these foreign chemicals, do they trigger something our system to go haywire, do they attach themselves to other cells in our bodies and then develop into our cancers? How do our cells respond to the toxic pesticides that are sprayed on the vegetables that we love to consume? Lactating mothers and pregnant mothers are told to avoid certain foods or to eat responsibly for the health of their child due to of the transmission of micronutrients or toxins. Why is it okay then to allow poisons to be sprayed on our food supply and think that it won’t be transferred into our bodies? Food should be our medicine but it no longer is what it should be and science has proven that.
    Mr. Naresh Gunaratnam thank you for being a conscientious healthcare provider, you have not failed, but perhaps those who regulate our laws that govern our food supply have.
    Ms. Terri Fuller

  • Angela,
    I too know a lady who passed in her late 40’s from a perforated bowel. I can’t believe that after posting your quote (copied below) you chose the colonoscopy. After all, why do GI Drs. make you sign a waiver to release all liabilities before the procedure. Colonoscopy is invasive and does have risks from the prep. from the sedation and the procedure itself-these are just plain facts. Below is your quote
    As, I had a relative twenty years ago who had a colonoscopy and ended up with a perforation- she lived in a rural area and alone but the good news was she got the all clear for being cancer free but died a few days later from her perforation.
    Colonoscopy is a great tool-for diagnosis-not for screening. Why do we do x-rays and CT scans before surgery? Colonoscopy is a surgical procedure.

  • Thank you Doc, this was an excellent article and I am glad I read it. I too was impressed with the Cologuard ads. I have a history of polyps and I now know this is not for me. Although I was told that in Europe they don’t do colonoscopies as a first line defense, I am glad that in America I have had the opportunity to prevent the occurrence of Colon Cancer in me.

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