In colonoscopy, quality is key to success
Dr. Wilson: You’re removing things and have no way of knowing in advance which are the bad ones and which aren’t.
Dr. Johnson, you’ve mentioned several times now that the quality of colonoscopy matters here. So, I’m intuiting that it’s not one-size-fits-all, that it’s not all the same. What do you mean by quality of colonoscopy, and what was it in the NEJM study?
Dr. Johnson: Quality colonoscopy is the quality of the whole process. It starts with the warm-up, if you will, and the clean out for the procedure. That allows the colonoscopist to be able to identify precancerous polyps, which we call adenomas (there are other precancerous polyps called sessile serrated lesions).
The identification of adenomas is extremely important. Even a small increase in the detection of those precancerous polyps has benefits. Well-performed studies looking at large databases show that a small, 1% increase in the adenoma detection leads to a 3% decrease in colon cancer and a 5% decrease in colon cancer–related death. There’s a huge array of effect when we talk about small increases in the adenoma detection rate.
Now, let’s go back to this study in NEJM.
If we base quality on the physician performing the colonoscopy, and say that the colonoscopy is achieving the act of getting all the way around the colon, but not all physicians in the study were able to do that, it starts to raise the question about quality, because adenoma detection is so important. Earlier reports from this group [Nordic-European Initiative on Colorectal Cancer Study Group] have shown that the adenoma detection rates have been way below the national thresholds. So, this raises the question of whether they found the polyp, and then whether they resected the polyp. They also don’t tell us where these cancers were. It is about the colonoscopy quality. It’s not the instrument. It’s the process.
An overview of other screening tools
Dr. Wilson: Dr. Lin, colonoscopy, which requires prep and anesthesia, is not the only colon cancer screening method we have. In fact, there are a bunch. I think we’re on board saying it’s probably better to detect colon cancer early than not detect it. But what are our other options aside from colonoscopy that can allow for early detection of colon cancer?
Dr. Lin: For most of my career, there were three options that I presented patients with. The first was the fecal test, which used to be in the form of initial hemoccult tests. These have been mostly replaced by fecal immunochemical testing. But they’re both just basically looking for the presence of blood in the stool. Anyone who has a positive test would be referred for a diagnostic colonoscopy.
The other test besides colonoscopy, which has been largely phased out in the United States, although it is still very much used in Canada and much of Europe, is flexible sigmoidoscopy. Until this study, the tests supported by randomized controlled trials were the fecal tests and flexible sigmoidoscopy.
Interestingly, there was a recent systematic review of flexible sigmoidoscopy looking at four trials and their effects over 15 years. They showed not only a reduction in colon cancer, but also a reduction in colon cancer mortality, and even a small reduction in all-cause mortality.
I believe three out of the four trials were done where the patients were consented and then randomized, so they had a higher uptake of the procedure.
But when you compare this with the colonoscopy trial, it really isn’t that impressive. You would expect a much larger benefit, because obviously you’re looking at the entire colon. But you really didn’t see that. It was, at best, maybe equivalent to sigmoidoscopy, but not a whole lot better.
Dr. Johnson: Perry, you mentioned sedation. It’s important to understand that this particular cohort of patients are from Norway, Sweden, and Poland, where it’s very much the norm to not get sedation for your colonoscopy. Any of the [audience] who have had colonoscopy will tell you that they are not ones to say, “Don’t give me sedation.” The rate of sedation is around 11% in Norway, maybe 23% in Sweden, and around 45% in Poland. So, the examiner and the patient were never really super comfortable.
I’ve done 50,000 colonoscopies in my career, and many nonsedated. We know that taking time increases the finding of polyps and the adequate identification and resection. So, that ability to perform at a high quality is very much impacted when the patients aren’t comfortable.
Dr. Wilson: Dr. Johnson, we brought up flexible sigmoidoscopy. For the patients watching whose doctors are talking to them about screening colonoscopy, what’s the difference?
Dr. Johnson: Flexible sigmoidoscopy is just a short scope examination, in which you see about one-third of the colon. I’ve been in the field for 45 years, and during that time we’ve seen that there’s a progressive increase in the development of cancers above that bottom third of the colon to the higher end, the two-thirds of the colon that you would miss without doing a full colonoscopy. Also, flexible sigmoidoscopy typically does not get covered for sedation.
Again, if you do the exam and find something, then you’re going to have to come back and do an adequate resection with a colonoscopy. So, one-stop-shopping colon cancer screening is not about detection of cancer, it’s about prevention of cancer, and that’s what colonoscopy does.