I’m skeptical about … screening colonoscopies.

Medical screening tests harm more people than they help. It’s true, and like the sinking of the Titanic: “It’s a mathematical certainty.” Remember first that the goal of medical screening is to detect or prevent potentially fatal diseases in an asymptomatic population. And the reason most people in the population are asymptomatic is because they don’t have the disease in the first place. You have to screen many to benefit a few. For example, say you’re performing a screening test for a disease where the annual incidence is 45 cases per 100,000 people. Let’s assume the disease is a bad one where the 5-year survival when the disease has spread is only 10%. But there’s also good news; the 5-year survival when the disease is detected early soars to 90%, making it a good choice for screening so long as the test is capable of picking up the disease earlier than it would be otherwise. Overall, the chance of the disease killing any given individual over the next 5 years is only on the order of 0.02%, but this small number adds up over the course of many years so that the lifetime risk of contracting the disease is 4.5%. Sounds like this might be an optimal disease for screening, doesn’t it? After all, it’s common, lethal, and detectable.


Colon cancer cells.
(Credit: Nat’l Cancer Institute, Unsplash; national-cancer-institute-lsxKuARrQXI-unsplash)


Now as to the screening test, let’s assume it misses 5 of every 100 people who have the disease (i.e. the “false negative” rate is 5%). You’ll have to take my word for it that this is good number for a screening test. So while not perfect, it’s still pretty good. But there’s also a down side to testing. Let’s assume the test causes harm in some, on the order of 0.25%, and death in a very few, 0.03%.

So far it’s all just a bunch of confusing numbers. Now let’s apply them. The disease I’m talking about is colon cancer and the screening test is colonoscopy. And here’s how the math works out: screen 100,000 asymptomatic people to find between 40 to 45 cancers, most of which will be early-stage with a decent chance for cure. That’s the good news. Now here’s the bad news; to save those 30 to 35 people (not every person diagnosed will survive), the test will harm upwards of 250 people, meaning that for every 1 patient who benefits, between 7 and 8 will be harmed. What kind of harm am I talking about? Diarrhea and dehydration from the bowel prep before; colon perforation, anesthesia reactions, and the occasional heart attack during; and GI bleeding and pain afterward. Of the people suffering these complications, a few will have heart attacks and die, a couple will suffer fatal anesthesia reactions, some will develop congestive heart failure, a couple will die from hemorrhage, and a few more from peritonitis complicating a perforated colon. The chances of suffering a colon perforation from the test is roughly equal to the chance of having a colon cancer diagnosed by it. All told, you can expect 30 deaths per 100,000 colonoscopies performed, meaning that the death rate from colonoscopy is roughly equal to the number of cancer deaths averted through early detection. This is the dirty secret that the American Cancer Society never tells you when it advises that everybody undergo a screening colonoscopy starting at age 50.


(Credit: gis.cdc.gov/Cancer/USCS/DataViz.html)


So why are we doing screening colonoscopies at all? Well, colon cancer is bad news. It’s the third most commonly diagnosed cancer and the second leading cause of cancer death in the U.S., killing 50,000 Americans annually. Risk factors for colon cancer include: a family history of colorectal cancer, obesity, inactivity, smoking, alcohol (2 to 4 drinks per day increases the risk by 23%), and a diet high in red and processed meats. Most cancers occur after age 50, which is why this age was selected to initiate routine screening.


(Credit: gis.cdc.gov/Cancer/USCS/DataViz.html)


Here’s why I’m not ready to throw in the towel on routine colonoscopy screening: As opposed to most other cancer screening tests, colonoscopy has the ability not only to detect cancer earlier than it might be otherwise, but also to prevent cancer before it occurs. You see, colonoscopy—which refers to the insertion of a fiberoptic scope up the rectum into the large intestine after a thorough bowel prep to rid the colon of stool—is also the best test for detecting polyps, small growths that can occur along the lining of the bowel. Polyps are exceedingly common, occurring in more than a quarter of people by age 50, and the reason they’re important to know about is that a small percentage of them will turn cancerous over time. The process is slow, typically a decade or more, which explains why a person with a “clean” colonoscopy at age 50, doesn’t routinely need another one for 10 years. In almost all cases polyps can be resected directly through the colonoscope. It is estimated that widespread screening colonoscopy and polypectomy (polyp removal) has the potential to prevent 65% of all colon cancers. The downside to this approach is that most polyps will never become cancerous and close surveillance in those with polyps inevitably leads to more screenings, more colonoscopies, more expense, more anxiety, and more bleeding complications. And while it’s tempting to attribute the decline in the incidence of colon cancer (from 60 per 100,000 in 1975 to 45 per 100,000 in 2007) to screening, it’s important to note that this decrease started before the institution of widespread screening (which, by the way, is not so widespread anyway, with fewer than 60% of adults adhering to recommended practices—it seems people don’t like having things placed in their rectums, even for a good cause).

The American Cancer Society recommends at least one of the following screening tests starting at age 50 for all Americans:

  • Colonoscopy every 10 years or
  • Flexible sigmoidoscopy every 5 years or
  • Double-contrast barium enema every 5 years or
  • CT colonoscopy (also known as “virtual colonoscopy”) every 5 years

A flexible sigmoidoscopy is similar to a colonoscopy in that it involves the insertion of a fiberoptic scope into the rectum but to a lesser depth than colonoscopy (2 feet instead of 5, thereby decreasing the time, discomfort, and complication rate associated with the procedure). A double-contrast enema involves injecting barium, followed by air into the bowel via the rectum, before completing a series of x-rays to look for irregularities along the bowel wall. Positive x-rays are followed by a colonoscopy. Lastly, CT colonoscopy (not a colonoscopy at all) examines the bowel through CT imaging after a bowel prep and subsequent gas inflation of the colon through a small rectal tube. It is less uncomfortable than either a colonoscopy or sigmoidoscopy, but here again, positive studies require a follow up colonoscopy.


(Credit: cdc.gov/cancer/colorectal/basic_info/screening/tests.htm)



(Credit: cdc.gov/cancer/colorectal/basic_info/screening/tests.htm)


An even less invasive way to screen for cancer is through annual or biannual stool testing for occult blood. Here, the patient places a small amount of his or her stool onto a card which can then be tested in the doctor’s office for the presence of blood. Several cards per screening are recommended and, again, positive tests are followed by colonoscopy and endoscopy. The problem with this approach is that not all cancers bleed and not all blood is from a cancer. Thus, this form of screening involves a relatively high rate of both false negatives and false positives.


(Credit: cdc.gov/cancer/colorectal/basic_info/screening/tests.htm)


How good are the tests? According to a Cochrane collaborative review, sigmoidoscopy versus no screening lowered colorectal cancer mortality by 28%, while stool screening for blood versus no screening reduced mortality by 14%. Compare this to the 40 to 50% reduction in the incidence of colorectal cancer associated with either daily aspirin or exercise, however, and it becomes clear that prevention through a healthy lifestyle is much more effective than expensive screening tests.


(Credit: cdc.gov/cancer/colorectal/basic_info/screening/tests.htm)


But if the real point of screening a population for disease is to increase the life expectancy of the group as a whole then colon cancer screening fails. Despite what you might have heard from Katie Couric (who had her colonoscopy broadcast on the Today Show in 2000 to promote colon cancer awareness after her husband died of the disease), your family doctor, gastroenterologist, and the American Cancer Society, colon cancer screening hasn’t saved any lives. Life expectancy and all-cause mortality in people undergoing screening are the same as in people who don’t. The small reduction in colon cancer death is simply replaced by a slight increase in death due to other causes like infection, heart attack, stroke, and other forms of cancer. There is no long term survival benefit to screening. One possible explanation for this is that chemo and radiation are toxic forms of treatment that increase the risk of dying from other causes. Another is that bodies are designed to fail, if not from cancer then from something else.

Disclosure: I’m not advocating that you skip your colonoscopy. Readers should follow their doctors’ advice, but know that the evidence is not nearly as cut-and-dried as you’ve been led to believe. Lastly, although the Affordable Care Act mandated coverage of screening colonoscopies when performed for screening, if you choose to undergo a different form of screening like FIT-DNA (e.g., Cologuard) and the test is positive, the followup colonoscopy will not be covered as it is then performed for “diagnosis” rather than “screening.”


(Credit: cdc.gov/cancer/colorectal/statistics/use-screening-tests-BRFSS.htm)




  1. American Cancer Society, “Colorectal Cancer Facts & Figures: 2011-2013,” http://www.cancer.org/acs/groups/content/@epidemiologysurveilance/documents/document/acspc-028323.pdf.
  2. Oyvind Holme et al., “Flexible Sigmoidoscopy Versus Faecal Occult Blood Testing for Colorectal Cancer Screening in Asymptomatic Individuals,” Cochrane Collaborative, 2014; John Wiley & Sons, Ltd.
  3. “Final Recommendation Statement, Colorectal Cancer: Screening, October 2008,” United States Preventative Services Task Force, http://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFinal/colorectal-cancer-screening.
  4. Antonio Gimeno Garcia et al., “Public Awareness of Colorectal Cancer Screening Knowledge, Attitudes, and Interventions for Increasing Screening Uptake,” ISRN Oncology, 2014; v. 2014: ID425787.
  5. Aasma Shaukat et al., “Long-Term Mortality after Screening for Colorectal Cancer,” NEJM, 2103; 369 (12): 1106-14.
  6. Patrick Young and Craig Womeldorph, “Colonoscopy for Colorectal Cancer Screening,” Journal of Cancer, 2013; 4 (3): 217-26. *Best Review*

71 thoughts on “I’m skeptical about … screening colonoscopies.

  1. Well said, Dr.Clare. Very well said indeed. It’s wonderful to see someone who gives some reality based, common sense advice about this subject, and who, more importantly, doesn’t act as though colonoscopy is a harmless, routine test. Colon cancer is NOT a one size fits all disease, any more than any other type of cancer is. We DON’T all share the same level of risk for it, contrary to popular myth- and it’s nice to see someone who recognizes this.

  2. Failed to mention people with a family history or tall adult height. I wonder if there is a way to quantify how many people will die of colon cancer because this article conveniently gave them the permission they wanted to avoid the snake?

      • I’m do to have a screening on the 17 of aug. They found blood in my poo. I had an appointment with the specialist and every thing I ask to have it was no. I want to know if there’s anything out there I can have? Xrays, to see why I have blood. I’m a person that has had hemorrhoids almost all my life due to giving birth. My personal Dr. Said sure it could be from my Hemorrhoids. But get yr screening. What do you think

        • X-rays, standard CT scanning, and ultrasound are all inadequate to evaluate the source of rectal bleeding. A specialized type of imaging known as “CT colonoscopy” (discussed in the post) is an alternative, but much depends on your age, risk factors, amount of bleeding etc. I would heed the advice of your gastroenterologist.

          • Thank you for your response. I’m 68yrs. I’ve never had any bleeding. Nor having problems going #2 the.The home colon test did show blood. I’m scared to death about this Colonoscopy, I’m heart patient with a heart Fib doing excellent. They want to put me under. Which that scares me.

          • I understand your concern. Today’s sedation procedures for colonoscopy are very safe, but just to be sure, request to have the procedure done at a hospital (not the doctor’s office) with an anesthesiologist performing the sedation. This will ensure the highest standard of safety and represents the best place to have the procedure done should a complication arise. Good luck!

  3. Don’t ever drive a car, or walk in front of a bus, for that matter. My father never had a colonoscopy until age 75, when he ended up in surgery the next day, sporting a stoma and bag. He died 4 years later when it metastasized to his brain. My Aunt hadn’t had a colonoscopy in 20 years, and just had a stage 3 tumor, the size of a golf ball, surgically removed, and her colon resected. Please. The benefit far out weighs the risk. But do what you want. You’re free to choose. And by the way, don’t get a mammogram either. Come to think of it, skip your dental cleanings as well. I’m vegan, plant based, pill free, and healthy for my age, but I’m not stupid.

    • Thank you for taking the time to write. I am sorry to hear about the death of your father and your aunt’s unfortunate diagnosis. Anecdotal stories pull at our heartstrings. They provoke strong emotional responses, but they aren’t evidence. The truth of the matter is that the vast majority of people undergoing a screening colonoscopy will experience neither benefit nor harm from the procedure. In the few who have a cancer diagnosed at an early stage, the benefits loom large, but the real advantage to colonoscopy over other cancer screening tests lies in its ability to prevent a cancer before it occurs via removal of precancerous polyps. But there are also real harms associated with it.

      In your father’s case, it is entirely likely that screening would not have prevented his death. Assuming his initial colonoscopy at age 50 would have been normal, then he would not have undergone another until age 60, and then again at age 70. It is unlikely that the cancer that resulted in a colon obstruction at age 75 would have been detected five years earlier. It is possible that annual stool testing for blood might have allowed for an earlier diagnosis, or that polyp resection during an earlier colonoscopy would have prevented his cancer altogether, but it’s also possible that one of the earlier screenings might have perforated his bowel.

      It is estimated that roughly 282 patients need to be screened with colonoscopy to prevent one case of colon cancer and that 871 need to be screened to prevent one death (NEJM 2012; 366: 2345). Meanwhile, a recent review of more than 330,000 outpatient colonoscopies (Gastroenterology 2016; 150: 103) found that 1.6% of Medicare patients undergoing a colonoscopy wound up at the hospital within a week due to complications from the procedure (bleeding, abdominal pain, and bowel perforation being the most common). This equates to 1 in 61 colonoscopies resulting in harm. From this, it’s clear that more patients are harmed from colonoscopy than benefit from it, but since the harm prevented (cancer) is more serious than the ones caused (pain, bleeding, perforation), screening still makes sense for most people. It certainly does in your case where the family history of colon cancer is strong.

      Several studies have pointed out that both patients and physicians tend to overestimate the benefit of screening and underestimate the harm. When the topic is broached, it is usually in the terms of “risk/benefit.” This implies that there is merely a risk of harm and a certainty of benefit. It is more appropriate to discuss the topic in terms of “harms and benefits” or “the risk of harm and the possibility of benefit.” Semantics matter. The purpose of this post is not to dissuade anyone from undergoing a screening colonoscopy, but rather to invoke balance into the discussion. After all, patients certainly can’t be expected to give “informed consent” for a procedure about which they haven’t been informed.

      For those interested in this topic, I highly recommend two books by Gilbert Welch: “Overdiagnosed: Making People Sick in the Pursuit of Health,” and “Less Medicine, More Health: 7 Assumptions That Drive Too Much Medical Care.” Also, see my update on this topic from June 23, 2016.

      • Hi Dr. Clare, I am one of those patients who was harmed by a colonoscopy. My colon was perforated during the procedure and a titanium clip was used to close the perforation. My understanding is that the clip did not hold. I had to have emergency surgery and spent 7 days in the hospital, 2 in intensive care. It was the most miserable experience of my life. The pathology from my polyps came back as “bowel irritations,” not even true polyps, as I was told by the gi surgeon who handled my case. I am not in a high risk group at all, I.e., no family history, exercise, mostly vegetarian diet, don’t drink much or smoke cigarettes. I will NEVER get another colonoscopy unless the technology greatly advances in the next ten years. I just got out of the hospital this past weekend and I have good insurance, but I still don’t know how much of a financial burden will be placed on my family because this happened. I was under the impression going in that the biggest risk might be the anesthesia. I had no idea about the risk of perforation. I wish I had been better informed before this happened to me. Thank you for your article.

        • I am sorry to hear of your complication. It’s an exceedingly rare one. While a colonoscopy may save your life, the relative risk of harm in the form of a colon perforation is still higher than the relative chance of benefit in the form of detecting an early cancer. This is not my opinion; it is a statistical fact, and why I believe blanket statements that “everyone over the age of 50 should have a colonoscopy” are misguided. Informed consent and shared decision making between you and your physician are key.

          • The stats I have seen (on NIH site) indicate that one perforation occurs every 1,000 colonoscopies, with 1/1,200 when just looking at routine screening colonoscopies as those with IBS are at increased risk of perforation related to having IBS. I do NOT consider that exceedingly rare. If you drive in your car 3 times per day, then one year’s of driving would equal to about 1,100. So if you ended up requiring surgery after 1,100 trips in a car, I doubt that would be considered “”exceedingly rare.” Call it what it is: a risk of perforation about 1/1,200 for a routine screening colonoscopy, as “exceedingly rare is disingenuous ….. or flat out LYING.

          • A recent meta-analysis, reviewing outcomes of nearly 2 million colonoscopies, found an overall perforation rate of 1 in 2,000 (Am J Gastroent 2016; 111: 1092-1101). This is where we agree.

            As to your analogy comparing colonoscopies to driving a car, not so much. If the risk of a serious accident were 1 in 2,000, would you be afraid to drive your car once every 10 years, because this is the appropriate analogy here. Sure, if someone were to undergo 2,000 colonoscopies then the risk of perforation would be unacceptably high, but a 1 in 2,000 risk for any single individual does indeed qualify as rare for an invasive medical procedure (by way of comparison, the risk of coronary artery rupture during a heart catheterization is generally in the range of 1 in 250). You also seem to be missing the point of the post, which is to note that there are potential harms as well as potential benefits associated with colonoscopy, and that both deserve consideration before proceeding.

          • I have had three bad colonoscopies out of eight so far and I am 49 years old. I have Crohn’s disease so they want me to go in regularly. I woke twice during the exam and was in horrible pain one doctor gave me more medication and that fixed the issue, the other doctor refused and tortured me for the next 15 minutes hoping that the Versed would wipe my memory of it, well it didn’t I remembered and I flipped out. The third time I got C-Diff from the scope, I became ill 1.5 days after the exam. I will probably never go in again due to the poor care I got from those doctors. I plan to take my chances with cancer. I figure it will not be much longer before they perforate my colon, so I will stop while I am ahead in the game. Yea, its scary but so is the test. Until they find a better way I am refusing to have them. My doctor pressures me every time I go in to have one. They want me to go in every 6 months to a year and I said no way.

          • I am sorry to hear of your unpleasant experiences associated with the procedure, but your complaint lies with the doctors conducting the examination rather than with the examination itself. A skilled anesthesiologist can do wonders to make the experience endurable, if not enjoyable, while also freeing the gastroenterologist to concentrate on the procedure itself without having to also attend to patient sedation. If you choose to undergo additional screenings, be sure to request an anesthesiologist. It may not be covered under your basic insurance, but is well worth the extra expense given your past history. Although the incidence of colorectal cancer in patients with Crohn’s disease or ulcerative colitis appears to be declining, it remains much higher than in the general population, occurring in roughly 2.5% of patients after 10 years of disease, 7.6% after 30 years, and 10.8% after 40 years (Gastroenterology 2006; 130: 1030). Thus the recommendation for more frequent screening. The most recent policy statement from the American Society of Gastrointestinal Endoscopy from 2006, recommends an initial screening exam after 8-10 years of disease (Crohn’s or UC), followed by repeat colonoscopy every 1-2 years thereafter in patients with extensive disease (Gastro Endoscopy 2006; 63: 558). For those with mild disease or those in longstanding remission, screening needn’t be performed as often. For those at average risk, screening is recommended every 10 years, starting at age 50.

      • ” It is unlikely that the cancer that resulted in a colon obstruction at age 75 would have been detected five years earlier.”

        This is a pretty incredible statement. His dad was 79 when he died and you are saying a colonoscopy 9 years before would have not have changed the outcome. Sure it would if had been removed. Please clarify.

        • If the cancer occurred through transformation of a polyp AND that polyp was large enough for detection five years earlier AND the polyp had been resected, then, yes, the cancer would have been averted. The miss rate for polyp detection on colonscopy is between 6-27% [Gut Liver 2012; 6 (1): 64], while the miss rate for colon cancer is about 5% [Ann Gastroent 2015; 28 (1): 94]. Still, your point is well-taken. Roughly 90% of colon cancers arise from polyps, and it is believed that it takes roughly ten years for a polyp to become cancerous. For screening to be of value it must either detect and remove polyps prior to that time OR detect a cancer while it is still asymptomatic and potentially curable. Once symptoms arise, colonoscopy is no longer performed for screening but for diagnosis. Roughly 10% of colon cancers arise de novo and tend to be more aggressive and faster growing, so it’s not clear that this sort of cancer would have been detected five years prior because it likely wouldn’t have been there.

          No screening is perfect; a recent case-control review of colon cancer in Kaiser Permanente patients found that screening colonoscopy reduced the risk of colon cancer death by 67%, which still means that a third didn’t benefit from it [Gut 2018; 67: 291]. While this sounds like a striking reduction, it still requires screening roughly 870 patients to prevent one colon cancer death [NEJM 2012;360: 2345]. Overall, it’s not a high-yield procedure. Meanwhile, performing this number of interventions can be expected to harm two patients in the form of excessive bleeding or, less likely, colon perforation.

          So, while it is entirely possible that regular screening might have averted this gentleman’s death, it’s far from a certainty. Know that my comment was also made, in part, to assuage guilt on anybody’s part–there is no point in blaming the victim or his family after the fact. Again, the point of the post is not to dissuade anybody from the procedure, but rather to raise awareness of possible harms and alternative methods of detection.

  4. Thank you for this information. I was diagnosed with Crohn’s when I was 13 years old and am now 31 years old. Steadily over the years my symptoms and inflammation have decreased and my last colonoscopy almost 3 years ago showed no signs of inflammation or cell change. I have followed a mostly Whole Food Plant Based Diet for several years now, and am undergoing treatment for Lyme Disease (an old infection). My GI would like me to have a colonoscopy this coming June but I am on the fence about it. What are your thoughts with regard to screening for someone with non-active IBD?
    Thank you!

    • Patients with either Crohn’s disease or ulcerative colitis are at increased risk for colorectal cancer. That risk depends upon multiple factors including the duration of disease, the extent of inflammatory changes (dysplasia), and whether there is a family history of colorectal cancer. Current recommendations by the American Cancer Society are that patients undergo screening colonoscopy 8 years after initial diagnosis and then every 1-2 years thereafter, but you should know that in their 2010 consensus paper (available at http://www.gastrojournal.org/article/S0016-5085(09)02202-1/pdf) the American Gastroenterology Association specifically notes that patients with “…limited Crohn’s colitis do not require surveillance colonoscopy but should follow age-specific guidelines for CRC (colorectal cancer) screening.” The problem lies in that inflammatory changes associated with the disease typically take 8-10 years to develop into cancer, so that even if you are free of active symptoms now, your risk remains higher due to the symptoms you’ve experienced in the past. Shared decision-making between you and your gastroenterologist is the best approach here. Do not skip your appointment!

  5. Who can be certain of anything?
    Life is a chance. So, pray. Believe in God.
    Worry does not get things accomplished.
    Yes, doctors are only human. They are
    capable of errors. Just be positive.

  6. An interesting article!

    The literature is full of studies on screening colonoscopies, but much narrower on diagnostic colonoscopy. This is a completely unsubstantiated guess because I actually can’t find a good study, but I have to imagine the risk of complication in symptomatic patient is greater because of inflammation obstruction diverticula etc. Presumably the benefit is greater as well, because obviously there are many more patients with diseases that affect the large bowel than there are patients with neoplasms.

    • My post deals only with screening colonoscopies in asymptomatic patients. Diagnostic colonoscopies for symptomatic patients is an entirely different kettle of fish, but I agree that intuitively one would expect to find much higher rates of pathology likely accompanied by a slight increase in adverse events.

  7. This is Danielle again. My earlier response to your article was based in part on the fact that I personally know two people who were grievously harmed by colonoscopy. One of them almost DIED from it, in fact. He suffered a colon perforation during his test, and had to be rushed into immediate, emergency surgery to stop him from bleeding to death. When he woke up in the recovery room, his surgeon told him that he was incredibly lucky that he was still alive. He recovered from the surgery eventually, but he’ll be living with the after effects of that botched colonoscopy for the REST OF HIS LIFE. I NEVER WANT to be in a position where that will happen either to me or to someone else that I love, know, or care about. It’s NOT WORTH IT. … The point is that colonoscopy as a procedure isn’t without risk- and for some people, that risk is extremely serious. Apart from that, I have real problems understanding how ANY procedure with a false negative or MISS rate of between 30 and 40 percent ( according to the CDC’s website) can still be considered the gold standard when it comes to screening for this kind of cancer. The CDC obviously KNOWS about the high rate of false negatives which happen with colonoscopy, but they don’t publicize it because they don’t want to scare people away. And that’s WRONG, at least to me. People have a right to know what they are risking before they decide to undergo this, or any other screening procedure. After reading about this as part of my own research, as well as getting information from many other reputable sources, I decided that the stool based DNA test called Cologuard was the right route for me. I took it in January of 2017, and it was negative, just as I knew it would be. My PCP is still trying to convince me to have a colonoscopy done anyway, because he claims that “they can’t see the colon”. Well, duh- Of course they can’t. But that argument doesn’t hold water with me, because I’m like you, Dr.Clare. I don’t hold with the idea that the most dangerous symptom of all is no symptoms. That’s an attitude which promotes DISEASE, not HEALTH. It leads to over testing and over treatment, and puts people at risk of infections and death from procedures like colonoscopy which really weren’t necessary in the first place a lot of the time. And the sad reality is that colon cancer is like breast and prostate cancer in that it has become one of the most over diagnosed and over treated cancers out there. Yes, it’s bad news- but only for certain segments of the population. People need to stop treating it as though it’s a “one size fits all” disease, because it’s not.

    • Thanks for writing. You make some good points. The decision to proceed with colonoscopy should be a joint one made based upon the advice of your doctor, your personal risk factors for the disease, consideration of other options (like Cologuard), and your psychological make-up and risk tolerance. For most, the decision to proceed with a screening colonoscopy will be the right one. I am not advocating avoidance.

  8. Thank you for writing this article. I read it the day before my scheduled colonoscopy screening. I have no symptoms for any colon problems, and no family history. I had no idea of the risk/benefit ratio for someone with my background. I cancelled the procedure until I can talk again with my physician.

    • The point of my post is to foster a dialogue so that both patient and physician are comfortable with the potential benefits and harms. Just to be clear, I do not advocate for unilaterally skipping a scheduled colonoscopy

  9. This was a really interesting read. I’m not due for screening for another few years, but it looks like they’d have to take me off of my blood thinners and I’ve been wondering about the increased risk of clots and how that balances out with the risk of not doing the screening since there’s no family history. I’ll talk to my doctor when the time comes.

  10. This is a really excellent article. My two follow-up questions: what is the effect on all-cause mortality from colonoscopy? (I found this article by looking for just such a thing.) And what percentage of CRCs are found in the sigmoid colon vs. the 3/5 only reachable by colonoscopy?

    • Thank you. I am glad you found the post informative.

      In answer to your first question: There are currently no RCTs (randomized controlled trials) that have examined the effect of screening colonoscopy on all-cause mortality. There are several in progress (COLONPREV trial in Spain, the CONFIRM trial in the US Veterans Administration, and the NordICC trial) designed to look at the effects of screening colonoscopy on the incidence of colon cancer and colon cancer-specific mortality.

      With regard to sigmoidoscopy, there have been 4 trials with at least 10 years of data [the UK Flexiscope Trial, Italy’s SCORE trial, the US Prostate, Lung, Colorectal, and Ovarian Cancer trial (PLCO), and Norway’s NORCAPP], all demonstrating a reduction in colorectal cancer incidence in the distal colon (the region within the reach of the flexible sigmoidoscope), with cancer mortality reductions noted in 3 of the 4 trials. Unfortunately, none of the trials looked at the more important question that you raise; namely, does screening reduce all-cause mortality?

      But we are not utterly devoid of data here. The Minnesota Colon Cancer Control Study looked at fecal occult blood testing as a screen for colon cancer over 32 years of follow up and found that, although screening resulted in a lower colon cancer mortality (128 versus 192 deaths per 10,000 people screened), it had NO effect on all-cause mortality. People who didn’t die of colon cancer simply died at the same age from some other cause. Screening conferred no net survival benefit to the population. I suspect that if the same standard were applied to colonoscopy (comparing all-cause mortality rather than just cancer-specific mortality), the results would be similar. (For more on this topic, see my post “Update on Cancer Screening,” 6/23/16.) In support of this, the authors of an exhaustive 2015 review on cancer screening concluded that: “Among currently available screening tests for diseases where death is a common outcome, reductions in disease-specific mortality are uncommon and reductions in all-cause mortality are very rare or non-existent.” [Internat J Epidem 2015; 44(1): 264-77.]

      In regard to your second question: roughly 40% of colorectal cancers are located in the proximal colon (higher mortality) and, therefore, not amenable to detection through sigmoidoscopy (that examines just the descending and sigmoid colon). Cancer location varies by age and sex. For example, 57% of colon cancers diagnosed in women older than 80 are proximal, while just 26% of colon cancers in men younger than 50 are.

      Fortunately, for those averse to the bowel prep and subsequent placement of a scope up the rectum, a recent trial utilizing FIT-DNA (fecal immunochemical testing with DNA sequencing detection, e.g. Cologuard)–performed on stool specimens collected in the privacy of one’s home–found the test to be nearly equal to colonoscopy in detecting colorectal cancer [NEJM 2014: 370(14): 775-82]. So while colonoscopy remains the current “gold standard” screening test, there are new technologies available that will soon likely replace it. Meanwhile, the question of whether ANY cancer screening undertaken on an asymptomatic patient population confers an all-cause mortality benefit remains unanswered.

  11. Hello Bob,

    Thank you for the interesting article. I am a 42 year old female who had a colonoscopy and an endoscopy 3 months ago due to continuous abdominal pain after meals for a year and a half prior to it. A polyp was removed during it.
    I was treated for H Pylori after the colonoscopy and my stomach pain symptoms after meals disappeared.
    Now, 3 months after the colonoscopy that did not detect cancer, I started having blood on the surface of my stool. Given the pick-up rate of colonoscopy is not perfect, do you think I should insist for another one in case the first missed something?
    My family physician dismissed me after 2 minutes, saying it the blood was unlikely to be due to cancer, it must be internal hemorrhoids and did not order any further tests because my colonoscopy was 3 months ago. Note, I never detected blood in stool prior to the colonoscopy during all the 1,5 year of continual abdominal pain….I am not in pain anymore, but the blood worries me sick.

    • You are correct in noting that the cancer detection rate of colonoscopy is nowhere near 100%, but it is also true that the vast majority of bright red rectal bleeding is not due to cancer. Your primary care physician should have at least performed a visual exam and digital rectal exam. Most bleeding is due to common afflictions like hemorrhoids (both internal and external) or anal fissures. Cancer bleeding is rarely visible and typically detected after a fecal occult blood test is positive, followed by colonoscopy. Still, it is possible that a rectal cancer might bleed in the manner you describe. I suggest a follow up with a gastroenterologist to discuss your concerns. If no hemorrhoids are seen, an anoscopy to examine just the rectum, or sigmoidoscopy to examine the entire distal colon should suffice, or consider a stool-DNA cancer screening test like Cologuard. The worry associated with uncertainty is almost always worse than the testing needed to rule out the disease in question. Best of luck and thanks for writing.

      • I don’t blame you for being scared, Tina. I would be too, in your shoes. And forgive me for saying this, but I think you may want to consider finding another provider to be your family doctor. Any professional who dismisses, laughs off, or trivializes what is obviously a worrying symptom to you without even attempting to help or reassure you is no one I’d ever want to receive treatment from, that’s for sure. You may feel differently, though. Whatever the case may be, your doctor should be ashamed of himself, and at the very least, he owes you an apology for not taking you seriously. With that said, I’m with Dr. Clare- I think you should have a GI specialist follow up with you regarding your symptoms, because they clearly indicate that something is going on which shouldn’t be.

  12. Hi Bob

    I’m 50 years old female, self diagnosed lactose and gluten intolerant (bloating, abdominal pain, constipation or diarrhea if I eat gluten or non lactose free dairy). My question is does being gluten sensitive and lactose intolerant increase my risk for colorectal cancer? And if the answer is yes do you think the benefits of the colonoscopy out weigh the risks in my case, or do you think a fitDNA test like cologuard will suffice?
    Also have you heard anything about colonoscopies increasing the risk of appendicitis?

    • To my knowledge, neither gluten nor lactose intolerance increases your risk of colon cancer, but you note that these are “self-diagnosed” conditions. A colonoscopy in your case makes good sense, both to screen for colon cancer and to look for alternative causes of your gas and bloating. Cologuard appears to be an excellent screening tool for colon cancer, but is not yet ready to replace colonoscopy, as the latter possesses advantages that the DNA test doesn’t (e.g. polyp surveillance, polyp resection, and the capability to diagnose other conditions like diverticulosis and inflammatory bowel disease). Colonoscopy does not increase the risk of developing appendicitis.

  13. A VA doctor just told me that the VA is now recommending a colonoscopy as early as 45! After hearing about the risk of death from these invasive procedures, even as I am approaching 50, I am still debating whether to get one next year.

    • This is based on the recent change in recommendations issued by the American Cancer Society in May, 2018 stating that “screening should begin at age 45 for people at average risk.” This recommendation, in turn, was based on a review of epidemiological data showing that “Colorectal cancer incidence has declined steadily over the past 2 decades in the population aged 50 years and older because of the combined influence of screening and changes in exposure to risk factors, but there has been about a 51% increase in colorectal cancer among those younger than 50 years since 1994.” (CA CANCER J CLIN 2018;68:250–281). The change in recommendation was made based on this data, but because there are no long-term surveillance trials utilizing this lower cutoff, it remains a “qualified recommendation” as opposed to the “strong recommendation” issued for those age 50 and older. The report notes a higher incidence of colorectal cancer in blacks, American Indians, and Alaska natives. If you are a member of one of these groups then earlier screening is advised. As always, the decision the decision to proceed rests between you and your doctor.

  14. Bob, an interesting article indeed. I am a practicing internist in Florida. I take colon cancer screening seriously, as I have seen it’s devastating effects in both patients and loved ones. However, in the last twenty years, after routine colonoscopies, I have seen three patients with perforations requiring emergency surgery, one patient that bled heavily requiring transfusions after both of two seperate colonoscopies, one patient with a ruptured spleen that died, one with a splenic hematoma that survived, another that had to have Hep C and HIV testing after notification of an improperly cleaned scope, one that developed life threatening electrolyte disturbances after drinking the prep, and numerous patients that developed more minor problems such as post anesthetic brain fog, gas pains, altered bowel habit lasting for months, Etc. I still want to screen my patients, but I always felt there had to be a better way. And I just turned 50. I opted for Cologuard for myself, as I am at average risk. Fortunately it was negative. I have been advocating Cologuard for all my average risk patients now as an option in place of colonoscopy. The only drawback is the false positive rate that leads to a little over one in ten patients still needing a colonoscopy. But that gets almost 9 out of 10 patients out of doing the more invasive colonoscopy. That works for me. In addition, I know that the makers of Cologuard are working on a revised test with possibly better specificity and sensitivity. I also have a staff member who’s husband was diagnosed with stage three colon cancer just six months after completing a “normal” colonoscopy. The reported miss rate on colonoscopies is usually averaged to about 5% in the few studies I have seen. I have seen this first hand now. The ideal screening test should be cost effective, easy, safe, and have high degrees of sensitivity and specificity. I believe Cologuard has moved us closer to this paradigm in CRC screening. I can not wait for both the revised Cologuard test in the next few years, and for the studies that will follow on the effectiveness of Cologuard’s three year repeat protocol. I believe that will increase the tests sensitivity over longer time frames of screening. I have already seen one stage one colon cancer picked up by Cologuard, in a patient that had balked at doing a colonoscopy. That is truly a success story, if not anecdotal. Thanks for your thoughts on this complicated subject.

    • Thanks for writing. I appreciate your perspective. I agree that Cologuard appears to be an excellent screening tool without the inherent risks of colonoscopy. The major advantage of colonoscopy, however, has always been–and continues to be–its ability to prevent colon cancer before the fact, through polyp resection. Along with skin screenings, colonoscopy remains unique in this regard. Having said that, at age 59, I still haven’t had one.

      • The odd thing about colonoscopy however, is that they find poyps in 25% of those screened. The lifetime prevelance rate of colorectal cancer has been 3-4% or so for the twenty years I have been in practice. That’s been consistent over the last 25 years, long before colonoscopy took the lead in CRC screening. (Up to 4.5% in men now.) Those 25% or more of patients get locked in to successive colonoscopies every 3-5 years. The reality is that because of that, I estimate that over 50% of my patients end up on the five year plan. That’s about a minimum of 45% of my patients getting unnecessary procedures over and over. And between age 50-75, that could add up to six colonoscopies or more in a lifetime. It’s nice to remove cancers before they start, but when you have to do hundreds and hundreds of poypectomies to prevent one cancer, that leads to a lot of other risk.

        • You make some excellent points. Depending on which study you read, the lifetime risk of colorectal cancer in the US is approximately 4.2%, with 90% of these cancers occurring after age 50. Assume that you are a busy practitioner following 2,000 patients age 50 years and older. In this group, there will be about a 4% chance of developing cancer over 30 years of surveillance, meaning that 80 patients can expect to face the diagnosis. Assume that all of them undergo colonoscopy at age 50, where the incidence of polyps is reported as high as 40%. Of these, colonoscopy can be expected to miss roughly 1 in 6 polyps, leaving about 670 polyps detected on the initial round of screening. For the sake of argument, assume that all the polyps are large enough to recommend surveillance colonoscopies in 3 years. On follow up, 35% of these patients will again demonstrate 1 or more polyps, meaning another round of colonoscopies 3 years after the first, and so on, so that over 10 years of screening a total of 3000 colonoscopies will likely be needed. In this cohort, roughly 30 patients can expect to experience complications from the colonoscopy like pain and bleeding serious enough to send them to the ER, (Ann Int Med 2009; 150: 849) while 1 or 2 will experience a perforated colon from the procedure (Am J Gastroent 2016; 111: 1092). The mortality rate associated with colonoscopy is on the order of 0.02%, or 1 in 5000. Extending these numbers out over 3 rounds of surveillance and you can expect roughly 90 ER visits, 5 colon perforations, and 2 deaths related to screening. On the plus side, since approximately 80% of colon cancers arise from pre-existing polyps, resecting all of them has the potential to prevent roughly 60-64 colon cancers, and 20 deaths. The reports I have read cite a 10% polyp to cancer transformation risk over 10 years (thus the 10-year recommendation between screenings if no polyps are detected).

          In order to balance the benefits and harms, the goal should be to lower the number of people requiring 3- or 5-year surveillance colonoscopies, as this group is the one most likely to suffer complications from repeated procedures. The use of a DNA test, like Cologuard, isn’t quite ready for prime time as it misses more than 30% of high-risk polyps and nearly 60% of large polyps overall (NEJM 2014; 370: 1287). Suspect it remains the next-best option for those unwilling to undergo colonoscopy. These tests are certain to become better (more sensitive) over time, limiting the number of false negatives, but I don’t believe they are there yet. (For an excellent review on polyp surveillance, see: World J Gastroent 2016; 22: 1925.)

  15. Bob, I apreciate you running those numbers above. But there are several assumptions made that don’t pan out in clinical practice. Number one, the compliance rate with colonoscopy is about 40%. Mostly because people fear the test. That significantly changes how effective colonoscopy can be. 33% of people get no screening at all. And according to the CDC, of the two thirds of patients that do get screened only 62% opt for colonoscopy. That’s where the total of 40% (of total screenable patients) comes from above. In terms of Cologuard, they will need to have better compliance than with colonoscopy to be effective but I think they have a good opportunity to do just that. I would like to see both higher sensitivity and specificity, but they have gotten close enough even now to have a viable product. And I know they are working on adding further DNA markers to this goal. But I think Cologuard’s true value will be realized in the three year return protocol. If it misses 30% of high risk polyps, those with significant atypia or dysplasia, it has the chance to catch them three years later as a similar polyp, or a lower stage treatable cancer. Of course I realize these longer term studies remain to be completed, but I am optomistic that the outcomes will be positive. But if colonoscopy misses a polyp, esp the sessile serrated adenomas which are very difficult to see in the proximal large colon, that patient has to wait ten years for the next opportunity. I respect your opinion and comments, but I hope you keep your eye on Cologuard down the road! I think it is an exciting time in early cancer diagnostics. And in my own practice, in the first year of Cologuard’s launch, I was able to screen over a hundred patients that had never been screened before. Of those about 12 were positive, and half of those on subsequent colonoscopy had either sessile serrated adenomas (which do not generally bleed, and are missed by FIT), and tubular adenomas. Thanks again for you input.

    • Great points and I appreciate your sharing your real-life practice results with Cologuard. Thanks for reading and writing. I have a strong feeling that your patients are in good hands.

  16. My wife is having one right now. They want me to do one and I dont want to. I am 68 with NO history of cancer anywhere in my family. I am otherwise healthy and dont want to undergo the risks.
    I think this is a BIG money maker and they scare the shit out of you with the poop on a stick and positive for blood.
    I just dont want to do it.

    • This post is not intended to persuade or dissuade anyone from undergoing a colonoscopy, but rather to present data so that folks can make up their own minds in an informed manner based on their own tolerance for risk. There are benefits and harms associated with colonoscopy, but there are also benefits and harms associated with opting out. As I tell my patients, “You’re the boss of you.” Please openly discuss your concerns with your doctor. There are alternatives for those unwilling or unable to undergo the procedure.

  17. Interesting read, thank you. I’m on the fence, my doctor recommends a colonoscopy it seems to me like overkill. I’m asymptomatic of cancer am 29 years old and he prefaced the conversation of a colonoscopy with it’s probably hemorrhoids but let’s do one to be sure. Seems to me to be an odd test for something that is likely hemorrhoids, can’t they just look to confirm that. All my pressure is in the anal canal and it’s improved with diet, exercise and metamucil in just the two weeks since scheduling me one. It’s supposed to be done this week and family and friends are making me feel foolish for not wanting it done, since I’ve been dealing with changes in stool and bright red blood sporadically for two years, but the rate of incidence is hard to just read about in medical journals and look over. Obviously the odds something happens to me are low and peace of mind for 20 years has its benefits, but having kids I don’t want to get something done that could put me in more harms way. I’ve asked about other tests to confirm that it’s just hemorrhoids and kind of got the “well we could do that but I’d rather be thorough and recommend a colonoscopy” response. It all feels like a money grab to go to the gastro, get told its probably hemi’s and then without even looking get a scheduled colonoscopy.

    • The incidence of colorectal cancer in people younger than age 50 has been rising for several decades. The reason(s) for this are unknown. In all other age groups, the incidence of colorectal cancer is on the decline. Still, this needn’t overly worry you. According to data from the Surveillance, Epidemiology, and End Results (SEER) Program the incidence of colorectal cancer in people in their 20s is a mere 1 in 100,000 (J Natl Cancer Inst 2017; 109: djw322). Before undergoing a colonoscopy, your physician should perform a rectal exam to look externally and feel internally for hemorrhoids. Since you note that the blood is “bright red,” this indicates that the source is almost certainly near the rectum. If the source is not apparent on this initial exam, then anoscopy would be the next appropriate step in your evaluation. During this procedure, a short rigid instrument is inserted into the rectum allowing the physician to visually inspect the internal mucosa of the anus. Only after the completion of these tests should you be referred for a more invasive procedure like sigmoidoscopy. Best of luck.

  18. I was taught in the 1970’s that for “profit” medicine was going to dominate the health care industry someday and destroy the basic fabric of the doctor-patient relationship. Unfortunately this has come true and i am sure that the recommendations for screening are generated by the instrument makers, owners of ambulatory surgical centers and the gastroenterologists themselves.
    Public fear of disease unnecessarily has driven an industry rather than a genuine need for innumerable unnecessary surgical procedures. Hopefully the future will bring non-invasive less risky procedures to screen for a disease that has not prolonged the life of as many patients as we have been led to believe.

  19. I truly am grateful that I found this article today. I am schedule for an endoscopy and colonoscopy tomorrow. I’m 32 years old, I smoked for 10 years but haven’t in 4. I sit at a desk all day and try to eat a healthy diet but do not succeed very well. I was diagnosed with IBS this past year and have chronic bloating. I have dairy and gluten allergies but do not have celiac. I’m now nervous to follow through with these procedures as I don’t want to risk perforation but also don’t want to continue with the chronic bloating and constipation all the time. What is your opinion?

    • I’m afraid I can’t render a very informed opinion based on the limited data provided other than to note that in the vast majority of young patients with chronic bloating and discomfort the tests you mention (endoscopy and colonoscopy) are generally normal or non-diagnostic. This should not be taken to mean that there is no value to them. If nothing else, documenting normalcy will provide peace of mind. The incidence of colon perforation is on the order of 1 in 2000. The incidence of colon cancer in your age group is far lower than this, but the tests also have the ability to diagnose other more common gastrointestinal ailments like polyps, reflux, peptic ulcer disease and diverticulitis. Hope this helps and that you find a solution to this vexing condition.

  20. Dr. Clare,
    I had sigmoidoscopy at 35 ( anal fisure, the rest negative), and then full colonoscopy at 45, due to severe fear that my stomach issues were cancer. That colonoscopy was all negative, and I was diagnosed with IBS. I kept my IBS pretty much under the control, but I have very high anxiety and O severe OCD. My IBS worsened 2 and half years ago, because I got C DIff infection due to 2 antibiotics at the same time (clindamycin and amoxicillin – and got them, to be honest, for no reason whatsoever). C DIff was successfully treated with Vanco, but IBS persisted, sometimes worse sometimes better. I also developed fear of food due to C DIff PTSD-like trauma. Since it has been 12 years since my negative colonoscopy, and 2 and half years since my negative FOBT, my doctor recently opted for Cologuard. I am currently waiting for the results, but , since I suffer from serious anxiety, this waiting has wracked havoc on my general healt – the fear is overwhelming. I know you cannot give medical advice like this, but , just because I am so scared, what do you think my chances for Colon Cancer are, based on all this? I read German studies that claim that most people with completely negative colonoscopy may not need another one for 20 years – if ever. Also, I am what you would call, average risk. Thank you so much !

    • Sorry to hear of your difficult struggles with IBS and C. difficile, but you are to be commended for overcoming your fear and undergoing a Cologuard exam. The fear of a bad outcome causes many people with anxiety to forego care altogether–never a good thing. Based on SEER data (Surveillance, Epidemiology, and End Results), the annual incidence of colorectal cancer in people aged 55-60 is on the order of 30-35/100,000, or 0.03-0.035% [J Nat’l Cancer Inst 2017; 109 (8): 1-6]. Looking at this from a glass half-empty/half-full perspective, your glass is nearly full to the brim. “If you are depressed, you are living in the past. If you are anxious, you are living in the future. If you are at peace, you are living in the present.” – Lao-tzu. A walk in the woods is a wonderful way to live in the present (even better if you bring a dog along!). Best of luck.

  21. I had a 52 year friend die from a colonoscopy. He was a healthy competitive swimmer. After this his cause of death was listed as a stomach infection, because they prorated his colon. Do we really know the truth of much harm is done by colonoscopy?

    • Actually, the incidence of harms associated with screening colonoscopy are well established. The most recent US Preventative Services Task Force review on this topic published in 2016 looked at 26 trials, involving more than 3.4 million screening colonoscopies, and found a perforation rate of 0.4 per 1,000, and a GI bleeding rate of 0.8 per 1,000 colonoscopies performed for cancer screening (JAMA 2016; 315: 2576). Earlier this year, another review looking at more than 1.5 million screening colonoscopies performed over 6 years in California, reported an even lower perforation rate of just 0.29 per 1,000 procedures. The overall complication rate in the study, that included the incidence of heart attacks, strokes, and serious adverse gastrointestinal events (perforation and bleeding) within 30 days of the procedure, was a mere 0.53 per 1,000, a number in line with the incidence of adverse events after other minor surgical procedures like joint aspiration, arthroscopic knee surgery, or cataract surgery (Gastorenterology 2018; 154: 540). These studies, that involved huge numbers of patients, found a lower incidence of adverse events than previously reported, suggesting that the procedure has grown safer over time. The risk associated with a single colonoscopy to any given individual is small. What happened to your friend is tragic but distinctly uncommon. Meanwhile, the American Cancer Society estimates that there will be 50,630 colon cancer deaths in the US this year. Choose wisely based on your own tolerance for risk.

      • According to idataresearch.com roughly 19 million colonoscopies were performed in the U.S. at an average cost of $3,081 for a total of $58.5 Billion dollars. Man, colonoscopies are BIG business, particularly considering its questionable screening effectiveness in reducing deaths as well as its imparting harm to some patients. If my math is right, according to your figures, there are up to 7,600 perforations each year as well. I think I’ll stick to my healthy vegan lifestyle and go with an annual stool test. I’ll take the risk of an invasive colonoscopy only if symptoms arise that warrant it. Big business and healthcare are not a good mix for blindly entrusting my health and well-being to.

        • No argument from me that colonoscopies represent “big business,” but I will quibble with the implication that it’s about money and not about health. Every gastroenterologist I know believes in the value of colonoscopy to diagnose and treat diseases of the GI tract. And they’re not wrong. The costs may be exorbitant, but that is not the point of the post. Little argument that a healthy lifestyle is the best defense against cancer (and almost all other chronic diseases, as well). Thanks for your comment.

  22. Thanks for a great article,
    The research you mentioned that claims no increased life expectancy from screening was dealing with Screening for Fecal Occult Blood
    However, according to another research colorectal cancer screening does increase life expectancy:
    What I myself don’t like about this research is data contamination from people who have family history of cancer or other symptoms that indicates high probability of cancer.
    What is the advantage of colorectal cancer screening for the rest of us? I’m not sure.

    • The study you cite did NOT show a reduction in colon cancer deaths associated with colonoscopy. Per the authors: “The purpose of this study was to assess the effect of screening for colorectal cancer on life expectancy and estimate the number of colonoscopies needed per life year saved.” This was a study to estimate the potential of colonoscopy to increase life expectancy, estimates not borne out in real-world studies looking at all-cause mortality. It’s also not appropriate to look at whether colonoscopy screening simply reduces colon cancer deaths without also looking at all-cause mortality. If screening results in a slight decrease in cancer deaths that is equally offset by a slight increase in deaths from other causes, then the screening offers no net benefit to society. It’s shocking but true nonetheless, that there are no trials demonstrating an all-cause mortality benefit associated with any type of cancer screening, be it breast, prostate, or colon. For more on why this is true, see my post “Update on Cancer Screening,” 6/23/16.

  23. After negative results over 35 years from 2 sigmoidoscopies, FIT tests, and one Cologuard test in 2015, I got a positive from a recent Cologuard test, however provided with great difficulty and stress (i.e. worst constipation ever, and I rarely suffer from that, as I have maintained a high-fiber diet for decades). I was concerned that this might have produced some bleeding, but sent in it anyway. Subsequently I have gotten negatives from 6 EZ-Detect tests (FDA approved) and from another FIT.
    When I requested Exact Sciences to parse the Cologuard results: positive for FIT, for DNA, or both, they refused my request. That is one horn of my dilemma.
    The second horn is my options, given that I am in all the population cohorts for greater risk for perforation or other serious events at colonoscopy: female, lower BMI, old age (78), post-hysterectomy, daily aspirin, endometrial carcinoma (no recurrence) in 2015, frequent small pains that suggest adhesions or colonic twists at either the sigmoid-descending colon juncture or in the transverse colon — pains are a moving target, usually a small tender or sore spot on the center-left abdomen.
    Oh, one other thing: my relatives have mostly died at 90+ years. No one among my ancestors or distant relatives has ever had colon cancer.
    I am considering (1) taking a FIT test every six months; (2) repeating Cologuard, though with some skepticism about the company; (3) colonography, although some studies show almost as great a risk for perforation as at colonoscopy; (4) colonography with same-day option for colonoscopy, offered by Cleveland Clinic and elsewhere; and (5) colonoscopy, IF I can find a gastroenterologist in whose hands I am willing to place myself.
    Your reaction to this complex set of options would be very welcome.

    • You are certainly on top of things and have summarized your situation and dilemma beautifully. I am not qualified to render an expert opinion given your situation. I do not know the false positive rate associated with Cologard, but certainly their response to your query was less than ideal. The multiple negatives tests are reassuring, and this points out one of the problems associated with screening in general. Once a test is positive, it’s very hard to convince yourself that you don’t have the disease being screened for. One study looking at the harm associated with false positive mammograms noted that negative psychological effects, like anxiety and depression, lingered for a full 3 years after the initial test, irrespective of negative follow up testing. This remains a difficult issue. Best of luck for your future health.

      • Of note, Exact Sciences is working on a new Cologuard test that deletes the FIT component altogether. Preliminary study results should be available in 2020. This will allow the return time window on the kits to be six days instead of the current three days. The FIT component was the time limiting factor on kit expiration. In early studies from what I have heard, the “Cologuard 2.0” will have a much lower false positive rate. That is one of their main goals. We should see specificity increase above 90%, and if all goes well, we may expect a higher sensitivity as well. I am cautiously optimistic while awaiting these results. The false positive rate is Cologuard’s weakest attribute. But still, it gets 87% of people out of doing a colonoscopy! Or at least out of doing a colonoscopy that would have been completely negative anyway, as many patients with a positive Cologuard will be found to have potentially pre cancerous polyps. Andrew Conti MD

    • The false positive rate for Cologuard is 13% based on a ten thousand plus patient study from 2014. Positive or negative results are based on a proprietary algorithm of 11 DNA markers and a FIT or fecal blood test. The FIT component can not be seperated out. It is possible to have a positive FIT component, and no DNA positive markers, and have a negative test. It is also possible to have a negative FIT component and enough positive DNA markers to render the test positive. The false positive rate, while on avg is 13%, is actually a lot lower for younger patients, and higher for older patients beyond 70. That is due to the natural aging process and changes in DNA methylation of cells that line your colon. Cologuard is particularly good at picking up cessile serrated adenomas on the right side of the colon, a type of pre cancer that does not bleed much. If you had a positive Cologuard, the fact that you do not have blood in the stool is irrelevant. Not all cancers bleed. In fact Cologuard picks up over 94% of stage 1-2 colon cancers. The FIT stool blood test picks up only 73%. FIT misses nearly all sessile serrated adenomas, even advanced ones headed towards cancer. Hope this helps. Andrew Conti MD

  24. As you note, anxiety and depression have dogged my days ever since I made this big mistake. If I give advice to my relatives, I think they should order a FIT test first, make sure it’s negative, and then send in their Cologuard test. At least that way, if the results are positive, it is likely that DNA changes are signaling a potential cancer.

    I checked on the Cologuard test studies — false positive rate is 13%. Not very reassuring.
    The false negative rate, however, is quite low: 0.06% chance of cancer but still, 34% chance of precancerous polyps.
    Cologuard has a 42% rate for detecting advanced adenomas.
    The statistical problem, though, is that colonoscopy is a lot riskier for women, former abdominal surgery patients, and even people of normal weight! The best rates I found were from Kaiser Permanente, 1: 3750; the worst from California Medicare: 1:1300 (but comparing all people with only >65).

    Many thanks for your kind reply.

    • Margo, compare Cologuard’s false positive rate of 13% to Colonoscopy’s false positive rate. Colonoscopy finds polyps 25% of the time, or greater. Yet very few of us ever end up with colorectal cancer. Between 4-4.5% of us to be exact. That tells us that the vast majority of polyps removed are essentially false positives. The trick is in knowing which ones will become cancerous later. That is the crux. Cologuard can be used as a way of stratifying our risk ahead of a more invasive test such as colonoscopy. Someone with a positive Cologuard is far more likely to have an advanced polyp with dysplasia, or a colon cancer on subsequent colonoscopy. But even the majority of positive Cologuards will not end up with colorectal cancer on colonoscopy. No screening test is perfect. But some are certainly less invasive than others.

  25. This is an excellent discussion. While struggling with the decision, myself, I researched the medical literature and worked the numbers, and came to the same conclusion as Drs. Clare and Conte, which is how I found this blog.

    Then I googled colonoscopy lawsuits and was absolutely astounded by what I found. Thousands of hits recounting horrifying stories of healthy people who had undergone the procedure and died tragic deaths. Is it really preventative medicine if it isn’t guaranteed to cause no harm or prevent death? And why shouldn’t the medical community stand behind their assertions and assume the risk for recommendations they insist are well-reasoned and in the best interest of their patients?

    So I reframed the situation and reversed the odds. If I had only a 4-5% chance of winning the lottery, would it be in my best interest to bet 95% of my savings on a ticket? No, those are lousy odds! Therefore, is it logical to bet a 95% chance of health to erase the 4-5% odds of illness? Of course, their is no real winning in the game of life; something is going to take you out, and there is simply no way to predict who or when a terminal illness will strike. I know athletic people who have died young of heart attacks, while obese friends have lived longer. I know non-smokers who have lung cancer and smokers who have lived until 90. It seems unethical to me to scare people into a risky elective procedure based on emotion, so that others can profit, regardless of the outcome. If logic doesn’t prevail and the medical community refuses accountability, then the motive has to be financial, and this is why so many people distrust them. Their recommendation: Risk 95% to win 5% so they can 100% profit.

    • Search Google on any topic and you will find anecdotal stories that will scare you. For every colonoscopy horror story, there are many more horror stories about actually having colon cancer. That is why randomized controlled trials are necessary–to more accurately ascertain the benefits and harms of screening and treatment. The purpose of this post is to shed light on uncertainties and the potential harms of screening that are swept under the rug with blanket statements like “Colon cancer screening is a no-brainer.” To the contrary, I encourage everyone to use their brain to make the best decision for his/her individual health. I do not subscribe to the notion that screening is financially motivated. I don’t know any gastroenterologists performing colonoscopies outside of recommended evidence-based guidelines just to line their pockets. Not one. Feel free to quibble about the data but please don’t suggest that doctors are performing colonoscopies just to send their kids to private school. Skepticism is healthy; cynicism isn’t.

  26. At the age of 55 I had some small polyps removed during a screening colonoscopy. I had no symptoms but was at the age where the doctor recommended I do the test. 6 years later I had another colonoscopy where they removed some more small polyps that were adenoma type. Now at age 65 the doctor wants me to do another colonoscopy and I am very uneasy about doing it again, I have no symptoms of any sort either. When I read that the screening has as yet not saved lives – I wonder what the point is to put myself through another procedure that could cause me harm. Any thoughts for those of us who have had small adenomas removed in a previous screening. Are the outcomes for us different than in regards saving lives?

    • The concept of screening it a difficult one. While it is true that no studies have demonstrated a life-saving benefit to cancer screening when applied across POPULATIONS, that doesn’t mean that screening has no value when applied to INDIVIDUALS. In your case, colonoscopy might have already saved your life by removing polyps prior to them becoming cancerous. Recommended screening is every 10 years if no polyps or worrisome lesions are discovered on the initial screening, but that interval drops to 5 years when polyps are discovered because of their ability to undergo cancerous transformation. The presence of polyps increases your risk and regular colonoscopies reduce it. Your doctor is correct to recommend a repeat procedure. Best of luck.

    • Dr. Clare, it has now been about four years since writing this article. I am wondering if you are still on the fence concerning screening colonoscopies or if you have since gone forward and opted in. I am very much interested in your reasons if you decided to go forward.

      • The purpose of the post was not to endorse or deny the value of colonoscopy, but rather to inform people about a few of the nuances of cancer screening, in general, and colonoscopy, in particular. I am not a gastroenterologist nor an oncologist. I claim no particular expertise in this field other than intellectual curiosity. Over the course of my career, I have found that the benefits of any specific technology or treatment always receives the lion’s share of attention with scant scrutiny–if any–paid to the harms. I don’t blame physicians–they often don’t know the harms–as pharmaceutical companies and medical device manufacturers go to great lengths to de-emphasize potential concerns. Trials with positive results are far, far more likely to find a publisher than ones with negative results, particularly if the trial was industry sponsored. I don’t necessarily blame industry for this either–it is their job to sell a product. (But I do blame physicians and industry when they falsify, intentionally ignore, or bury data relevant to patient care.) The system we have is not pure, but when it comes to the specific topic of screening colonoscopies, I don’t believe the public has been intentionally misled. A closer look does suggest a relative lack of emphasis given to the harms of the procedure. Thus, a bit of skepticism remains in order. Patients cannot possibly be expected to give “informed” consent if all they hear is the upside. Having said that, my personal decision to undergo or decline the procedure is not particularly pertinent. What I will say is that I haven’t seen any new data that contradict the findings of the original post. Does that answer your question?

  27. Dr. Clare,
    Thank you so very much for laying out the case regarding colonscopy! I highly commend you for telling the truth as you know it and encouraging honest discussion.
    Best Regards,
    David S.

  28. I think I read about 100 blogs today about pros and cons of getting a colonscopy. I am scheduled for my 2nd one which I had the first one 11 years ago. I am definitely on the fence about whether I want to proceed. I excercise with yoga and walk every day for better health and don’t drink or smoke. I have a problem with using the bathroom but I have found with some diet changes it helped me a lot which I suppose might be common sense. Frankly I am scared about what can happen during the procedure although those might be rare numbers but I don’t want to be one of those numbers. I have other chronic health issues which are under control but unsure if I will be affected during the procedure. So it is a tough decision to be made. Thank you.

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