COLONOSCOPY AND COLOGUARD

OK. Let’s talk about everybody’s favorite topic, colonoscopy.  If you are over 50, it is a good bet that essentially every time you see a doctor, you are asked when your last colonoscopy was, and if you don’t give the right answer, they try to shame you into getting one. 

I think we need to talk about three things:  why the doctors are always asking about this, what the value of a colonoscopy really is, and what alternatives now exist, primarily the new Cologuard test.

First, why do almost all doctors seem fixated on this unpleasant topic?  Yes, your doctor is concerned about preventive care.  Of course.  However, you need to recognize that physicians are now judged for what the Government, in conjunction with many insurance companies, consider the “quality” of your visit.  How do you judge the quality of a visit?  None of these authorities has really figured this out in any real sense, so they look at a checklist of actions they have rather arbitrarily deemed important, even if these have nothing to do with you or the problem you came in with.  One key checkbox is whether the doctor askes about your colonoscopy status.  It has been a standing joke among doctors for years that if you come in with a hangnail, and we do nothing about the hangnail, but can document that we asked about a colonoscopy, we will be deemed to have given you high quality care.  You gotta love the Government’s “experts.” 

Yes, this sounds like a joke, but unfortunately it is all too true.  So, please, give your doctor a pass on this one.  He is not really obsessed with colonoscopies, the Government is. 

So, what is the theory behind a colonoscopy?  Basically, it is well known that early colon cancers that have not yet spread outside the colon are very curable.  However, if it is left undetected, at some point the cancer will spread and become difficult to cure, and later on impossible to cure.  One aim of a colonoscopy is to find the tumor early so it can be successfully treated.  This can be done by inserting a long flexible scope through the anus and visually inspecting the inner lining of the colon.  This technology has been available for over 40 years.  If they see something that might be a cancer, they can use a long flexible biopsy forceps that feeds trough the scope to take samples.  These are sent to a pathologist, who will look at them under a microscope to determine whether they appear to be a cancer.  If they are, appropriate treatment can begin. 

A second aim of a colonoscopy is to try to prevent the development of cancers by finding polyps.  It turns out that a huge percentage of colon cancers begin in benign growths called “adenomatous polyps” which are fairly common.  These can be visualized with the colonoscope and removed with a snare. If the polyps are removed, they cannot possibly turn into a cancer. 

This is a great theory, but how effective is a colonoscopy in real life?  I think the best answer is that we think it is pretty good, but we do not really know, because it really has not been properly studied.  I suspect that you will find this fact as unbelievable as I do. 

So, just how effective is colonoscopy?  The figure you will often see quoted is that it detects 90% of colon cancers.  So far as I can tell, this number is fictitious and was just pulled out of the air.  This number may well be a good guess, but no evidence supports it.  And, how could anyone really know?  It is obvious that some cancers will be missed on any exam, but nobody is being subjected to a series or repeat colonoscopies just to see how may be missed.  This is why the end point for studies of this sort is the reduction of colon cancers that are eventually found in these patients.  Whether the cancers that do turn up were missed at the exam, or whether they developed after the exam will not be able to be determined.

At least three randomized studies are underway to try to ascertain the effectiveness of colonoscopy.  None has reported results yet.

SO, WHY DON’T PEOPLE GET COLONOSCOPIES?

The fact is, most people do not want to get a colonoscopy, and many will end up not being screened.  An article in Internal Medicine News found that only 38% of patients in the target age range got a colonoscopy when advised to, and even a major effort by the Kaiser group could only get to 66%. 

The disadvantages of colonoscopy are fairly obvious.  The prep is uncomfortable, involving taking medicines to induce an intense diarrhea the day before, so the colon will be cleaned out enough to give a good exam.  The procedure itself is uncomfortable enough that it is usually preformed with fairly heavy sedation.  Gaseous discomfort is the norm in the post procedure recovery.  It requires taking a day off work, and you need to have someone to drive you home afterward because of the sedation.  There are also potential complications from the procedure, including, in my experience, cardiac arrhythmias and perforations of the colon.  Perforations were seen in one study in one out of every 1750 procedures, ant these almost always require major open surgery, and often a colostomy. 

ALTERNATIVES TO COLONOSCOPY: 

Rarely discussed is the fact that there are actually several different tests that may be used to screen for colon cancer, and as of now there is no clear winner.  Let’s talk about the alternatives so you have some background when you end up choosing.

One that is rarely seen in the US now is called Flexible Sigmoidoscopy.  This is similar to colonoscopy, but it only examines the last portion of the colon, called the sigmoid colon, and does not look at the majority of the organ.  However, most cancers do develop in the sigmoid colon, and it is arguably somewhat easier on the patients subjected to it.  In the US, sigmoidoscopy has been almost entirely supplanted by the more invasive colonoscopy.  To date, there is no good study comparing the two procedures.  The colonoscopy may well be better, but the fact that the payment to the gastroenterologist is almost twice as high for colonoscopy might just have been a factor in the triumph of colonoscopy.   

The main reason to even discuss flexible sigmoidoscopy in this era is the fact that there actually have been randomized studies comparing its use with no screening at all.  In one such study, screening with the Flex Sig decreased the death rate from colorectal cancer significantly.   

The real take home message is that in certain age groups, screening is important. 

So, what are the other alternatives?  There are currently three approaches.  One, to mention in passing, is CT colonography.  This is an x-ray study that requires the same kind of prep as a colonoscopy, and which has not been well studied. Further, it is not CMS approved for Medicare and it is not covered by most insurances.

Next, There are several types of fecal blood tests that rely on the fact that cancers, and often advanced polyps, will shed small amounts of blood, which can be detected from a stool sample.  The tumors shed blood only intermittently, so the accuracy of a single test is lower than we might like, 73.8% in one study.  However, if this test is repeated annually, the accuracy improves.  One study shows that over a ten-year time frame, fecal blood tests give an accuracy equal to or better than flexible sigmoidoscopy.  The reduction in colon cancer incidence was 95% with the Fecal Occult Blood Test and only 82% with Flex Sig.  They have not been compared to colonoscopy.

It is interesting to note that most developed nations, including most in Europe, favor fecal blood tests over colonoscopy for routine screening, and the Canadian Task Force actually recommends AGAINST colonoscopy for routine screening, favoring fecal blood tests.  These recommendations predate the Cologuard.

The other alternative, recently FDA approved in the US, is called Cologuard.  This is a noninvasive test that takes a stool sample and analyzed for tumor DNA and also fecal blood.  In a study published in the New England Journal of Medicine, the Cologuard detected 92.3 percent of cancers and 43% of advanced polyps. 

This is a figure at least as good and the number quoted for colonoscopy.  An additional advantage of Cologuard is that it avoids the possibility of a complication of the colonoscopy.  Everyone worries about the discomfort of the procedure, but worse, on occasion, the colon is perforated, requiring open colon surgery for repair.   

The bottom line:   If you prefer the tried and true, get your colonoscopy.  I cannot tell you the Cologuard is as good as a colonoscopy, because the studies have not been done.  On the other hand, I cannot tell you that a colonoscopy is as good as the Cologuard test.  We do know that many people end up not getting the colonoscopy because of cost, worry about the discomfort, or fear. 

The one thing I am very sure of is that getting a Cologuard is better than NOT getting a colonoscopy.