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.

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  • While the author is correct in all the facts, I place a different emphasis on them and remind readers that there are some patients who for whatever reason cannot be persuaded to have the screening test of choice. As irrational as it may seem, these individuals are willing to take the risk that a positive result will end up requiring the same colonoscopy they are hoping to avoid. True, a 7% false negative rate is less than ideal, but we forget that numerous studies have found that colonoscopy itself is often ineffective in preventing interval cancers, especially in the right colon. If we are able to persuade a significant number of people to get screened who would otherwise not avail themselves of any screening modality, this benefit far outweighs the shortcomings of the Cologuard test. It is important to empress on our patients that due to its insensitivity to smaller lesions, it needs to be done more frequently than colonoscopy, probably at 3 year intervals. I, for one, encourage patients to consider Cologuard when, after a thorough discussion of the rationale and available screening techniques for CRC, still decline colonoscopy.

  • The real problem here is the marketing. There was a reason that marketing healthcare products used to be illegal. No one is weighing the extra deaths, or unnecessary procedures, to determine of the lower age, is due to profits or medically necessary. Thanks to a lot of misleading and outright deceptive media manipulation, people do choose to undergo this invasive and painful test, will find they might have to do it without anesthesia. The media has already broadcast the idea that people undergoing even more dangerous tests and procedures can turn people into ‘”drug addicts.” No agency is tracking how many people will just say no, even if there is a benefit.

  • Written by someone who thinks colonoscopy is 100% for detection. It is not. Not a single word about perforations during colonoscopy or the abhorrent prep. Written like a doctor whose income from colonoscopies is being threatened.

    • Hi Richard,
      I’m a gastroenterologist, and I make a living from colonoscopy. But I am very enthusiastic about Cologuard in the right setting for the right patient. I’m not worried about my livelihood. Like most of my GI colleagues, I want what’s best for my patients, no matter how the chips fall. But keep in mind that a test is not free of risk if it risks necessitating a procedure that does have risk. And yest, colonoscopy has risks, but failing to screen is far more risky.
      And by the way, all those Cologuards will keep us GI docs quite busy chasing down the positives, so any gastroenterologist with an eye on the big picture should see this test as a “win” for all concerned.

  • Funny that there’s no mention of the programmatic sensitivity of having 3 Cologuard tests within the same 10-year testing window of colonoscopy. Also funny that there’s no mention of colonoscopy’s cancer detection accuracy of ~ 95% vs. ~ 93% for Cologuard. Not much of a difference, and then you get another 2 cracks at it within a 10-year period. Pretty good, eh, doc? Also, you hammer on false positives pretty good, but as you know, the time and thoroughness of the scope increases significantly when a positive CG is referred for colonoscopy. Boy oh boy, there’s certainly a lot of bias in your article.

  • You write: ‘…and remove cancerous and precancerous growths called polyps if they are detected.’

    So both detection AND removal of polyps. Personal knowledge reveals that OCCASIONALLY polyp removal has caused serious harm.

    So focus just on polyps: Cologuard = 0 , but Colonoscopy = possible internal injuries. Which is better?

  • when I had my age 50 baseline colonoscopy, I had complications; had to go to the ER on a Sunday and missed a week of work.
    For my age 60 colonoscopy, I could face neither the prep nor the risk of complications. I have had acute chronic pain for 10 years, which resulted from a hysterectomy. I have other medical issues. I also can’t forget my baseline colonoscopy.
    I do worry that I didn’t have a colonoscopy, but for me, it was Cologuard or nothing. I just couldn’t face it. But I never heard of the other procedures in this article and my gastro doc never mentioned them.
    I’m on Medicare. Maybe Medicare doesn’t cover the other procedures so she never mentioned them to me?

  • I didn’t see any comparison of the hazards of either procedure. I wonder how many colonic perforations, bleeding incidents or infections are associated with Colonoscopy? (I really wish they had a RELIABLE method of sterilizing their tools, ewwww)
    Coloquards 93% efficacy seems a bargain when you include cost, safety and yeah – convenience…

  • Interesting, and I’m sure factual, article but I get a whiff, so to speak, of conflict of interest. I can’t help wondering if you make your living giving colonoscopies, finding polyps, and rinse and repeat.

  • I was not very surprised when I read that this article was written by a gastroenterologist. This article does not at all examine the true costs of Cologuard against a colonoscopy. In reality the “inconvenience” of a colonoscopy is very high. An entire day of sitting on the toilet plus an entire of day taken up by the procedure. The cost is thousands of dollars. I have heard many physicians try to wave off these costs by saying that they are covered by insurance or Medicare, but the reality is that we are paying for that insurance, and the insurance company is certainly not paying out more than we pay for it.
    This article does not examine the possible net benefit to people who do not go to regular screening colonoscopies, which is a very large portion of the population.

  • While this article is no doubt accurate about the limitations of Cologuard, I believe it fails to point out or even acknowledge that there are also issues/limitations associated with colonoscopies. People who have colons that have sharp angulation at the corners ( twisting ) can experience pain during and after the procedure AND sometimes the colonoscopy cannot be completed due to these conditions. He failed to acknowledge that or provide the statistics on that situation. He also failed to tell folks about the percentage of people that actually have/get colon cancer. Families that have a history of colorectal cancer certainly have reason to be concerned and tested and should no doubt try to tolerate a colonoscopy. But for others, Cologuard is a welcome respite for what is, for them, a painful procedure.

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