10 Things Changing the Face of CRC Screening
When thinking about colorectal cancer screening, the single most important thing that hasn’t changed over the decades is the importance of carefully inspecting the colon.
Nothing will ever replace how careful an endoscopist is, but newer adjunctive techniques and technology along with new recommendations have increased overall levels of screening and the yield of screening. In 2019, an armamentarium of options help us as gastroenterologists to screen for and prevent colon cancer.
From broadening screening criteria, non-invasive screening and improved bowel prep to using water and complementary in-procedure tools, we will review 10 things changing our daily practice, though it always comes back to the care and detail of the physician.
1. Younger Screening Age
One of the biggest changes recently was the release of updated CRC screening recommendation from The American Cancer Society in May 2018.
The long-standing recommendation – from the ACS, from U.S. Multi-Society Task Force (US-MSTF), the National Comprehensive Cancer Network (NCCN) and USPSTF – was to offer all Americans screening when they turn 50, regardless of family history or symptoms. However, the ACS put out a qualified recommendation to consider offering screening at age 45.
The reason for that is that although we have seen great successes in CRC incidence and mortality over the past several decades in those aged older than 50 years, there has been a steady increase in CRC incidence and mortality for those diagnosed aged younger than 50 years.
There are many hypotheses as to why we are seeing these trends, such as the increase in risk factors like obesity, sedentary lifestyles or changes in exposures, but the source of the increase is overall unclear. The ACS declared that regardless of the reason, the burden of disease in young patients is substantial to society and therefore we should consider screening earlier.
This recommendation is not yet incorporated into routine practice in part because it is new, but also because it has not been endorsed by the USPSTF, NCCN or MSTF. Nonetheless, it has generated productive discussions and important research on identifying patients at highest risk who may benefit from earlier screening.
Furthermore, the ACS brought public attention to the rising incidence and mortality in young patients, highlighting that CRC is not just ‘an old person’s disease.’ This announcement could spark discussions about colon cancer screening before patients turn 50 so we can identify patients to screen earlier based on family history and so patients do not delay cancer screening once they do turn 50.
2. Stool-based Tests
There are multiple CRC screening options that are endorsed by our professional societies. We divide them into stool-based tests – fecal immunochemical testing (FIT), which detects microscopic blood in the stool, or stool DNA, which is a combination of FIT and DNA markers in the stool – and structural tests. In a stool-based test, the rationale is that if you have a colorectal tumor, it may shed product into the stool.
The stool-based tests are designed to screen for CRC and they’ve been effective in doing so. In fact, multiple very large randomized controlled trials showed a significant reduction in colon cancer-associated mortality in populations screened by fecal-based testing.
In talking to patients, it’s very important to communicate that the different tests are designed differently. The structural tests such as colonoscopy and CT colonography screen and prevent colon cancer, whereas the stool-based tests are designed to screen for and find early colon cancers.
That said, the stool-based tests are extremely attractive. A colonoscopy is quite a process, requiring extensive bowel preparation, a day off from life, from work, finding child care or self-care due to sedation. It can be an extremely attractive option to do these stool-based tests in the privacy of one’s home without the need for any preparation, changes in diet or medications.
The other important thing to acknowledge and discuss with patients is these tests are just the first step in screening. All tests other than colonoscopy are two-step tests. FIT test has an 80% sensitivity and the combination FIT and stool DNA has a 90% sensitivity for detection of colon cancer, but if either is positive, it requires a colonoscopy and follow-up.
3. Capsule Colonoscopy
Video capsule colonoscopy is where a patient orally takes a capsule that captures images while traveling through the colon. It requires a more intensive bowel preparation than colonoscopy. Like the stool-based tests, this is also considered a two-step test in that if it shows a precancerous polyp or a colon cancer, it requires colonoscopy to visualize, biopsy and remove the polyp.
One of the limitations of the traditional capsule colonoscopy is the lack of maneuverability of the capsule. We are left to the patient’s own motility, so if the capsule travels through some areas too quickly, visualization can be impaired.
What has been an interesting development over the past couple years has been a magnetized capsule. Research is being done in a magnetized capsule where a physician can maneuver the capsule with magnets outside the body and pull the capsule in different directions to get a better look in the colon. This technology is still in development but has potential.
4. Improved Bowel Prep
One of the most critical pieces of a high-quality colonoscopy is bowel preparation, an area that has evolved quite a bit to improve tolerability and quality.
One of the most paradigm-shifting changes was to switch from ingesting the full prep the evening before a colonoscopy to a split-dose bowel prep where the patient takes half the evening before and the second half the morning of the procedure. This is now standard of care because it’s not only much easier for the patient to tolerate, but it provides a better quality prep. The second flush removes any last-minute residue building up in the colon.
More recent data showed select patient populations can do a modified low-residue diet the day before, ingest a split-dose prep the same day of the procedure and still achieve adequate bowel prep. This would minimize the disruption to the patient since all preparation is taken the same day of the procedure.
We also have a cadre of lower volume bowel preps, which are much more tolerable. Previously, patients would take an entire gallon or 4 liters of bowel prep, now there are options at half that volume.
5. Carbon Dioxide vs. Air
In terms of the colonoscopy procedure itself, there are wonderful advancements to make the process more comfortable for patients. First, most endoscopy practices do not use air inflation anymore. They use carbon dioxide.
Traditionally, with air insertion, the air could get trapped and make patients uncomfortable. Now, the carbon dioxide inflates the colon just as well to be able to see, but is more easily reabsorbed by the body. Patients complete the procedure and feel much more comfortable because they no longer have the air trapped in their intestines.
It, in fact, makes the procedure safer because it does not put as much tension on the wall of the colon, decreasing risk for trauma from the inflation – barotrauma – and more serious complications like tears to the colon or perforation.
6. Water Immersion, Exchange
Many endoscopists have also switched to water immersion for their insertion.
If you think about the colon like an accordion, the gas elongates it and makes it more uncomfortable for the patient and makes it more difficult for the endoscopist as it gives us more geography to navigate. If we keep the accordion decompressed and flood it with water, it’s a shorter distance for our scope to traverse and it keeps things decompressed, so it’s more comfortable for the patient.
Additionally, patients require less sedation vs. air insufflation. Patients wake up feeling more alert. With the use of this technique, we now could routinely offer colonoscopy without sedation for patients who prefer it.
The other technique shown to improve the quality of bowel preparation and detection of precancerous polyps is water exchange.
Not only are we putting water in at the beginning, we are suctioning it out. That creates a washer system that cleanses and washes the colon as we go. If there is any residual debris or mucus, it does a good job of cleansing that. In multiple studies now, it’s been shown to increase ADR.
It’s a very nice technique to add, especially if the bowel prep is hazier than we’d like.
7. Retroflexion, Repeated Views
The colon has dips, dives, folds and valleys that can be hard to visualize in totality. We often look several times in the same segment of the colon to ensure we optimize visualization. Changing the scope orientation, we can look several times in one part of the colon.
One way of orienting the scope is to create a rearview mirror, turning it so it looks like a candy cane and so that the camera is facing backward. Routinely, to try to improve polyp detection rate in the right side of the colon, the cecum, the ascending colon, endoscopists can retroflex the scope and get a nice look behind all these folds that a forward view may not offer.
Studies have shown this increases ADR, but the studies went on to show that any technique where you look multiple times, whether it be forward view and backward view or several looks with the forward view, increases ADR. That emphasizes my initial point that the care of the endoscopist is critical.
8. Endoscopic Attachments
Then we have adjunctive tools that can help flatten the folds to see on the other side and into the valleys. One of these is the use of a distal attachment cap, essentially a small plastic cap that we attach to the end of our scope to extend several millimeters and help splay down folds.
Similarly, an attachment that we can place on the scope that has prongs that keep the lumen of the colon open for us better is called the Endocuff (Olympus) and that has shown to increase polyp detection rates as well.
There is always emergence of these small, adjunctive techniques to improve quality of colonoscopy, but it certainly – at this point – will not replace a careful colonoscopist.
9. Chromoendoscopy, Dyes
Some polyps are very subtle and look like surrounding tissue. They can be very flat and difficult to detect. With these polyps, it is helpful to have something to improve contrast between normal vs. abnormal tissue.
Chromoendoscopy is a technique where we spray dye within the colon to provide enhanced contrast. It sticks to colon wall tissue differently when it’s a precancerous colon polyp vs. normal tissue. There are different dyes that are available to accomplish this, such as indigo carmine or methylene blue.
Data show use of this dye can increase ADR. It’s probably even more appropriate when we do find a polyp that’s very subtle, hard to delineate the borders, to use chromoendoscopy to enhance that polyp. Maybe chromoendoscopy didn’t necessarily help us find that polyp, but the dye is critical in delineating the border and confirming complete removal.
The point of colonoscopy is not just to find all these polyps, but to remove them so they don’t grow and turn into cancer. If we have an incomplete resection, which we know contributes to cancers occurring after colonoscopy, then we have done that patient a disservice. Chromoendoscopy is an incredible tool to help characterize polyps and ensure complete removal.
Specific patient populations benefit from chromoendoscopy. The average screening patient with a routine colonoscopy, may not benefit as much as high-risk patients, like those with chronic inflammation of the colon from ulcerative colitis or Crohn’s disease, and those with certain genetic or hereditary conditions with a high risk for fast-growing polyps such as Lynch syndrome.
10. Virtual Chromoendoscopy
Another technique that we use is virtual chromoendoscopy. Instead of spraying dye into the colon, often our scopes have a touch-of-the-button technology where we can change the light on the scope to improve our visualization.
For instance, Olympus manufactures a scope with a technology called narrow band imaging that filters light at 480 nanometers. This happens to be the same wavelength of hemoglobin, so it accentuates the blood vascular pattern on the colon surface.
Studies have shown this technology increases the rates of small polyp detection just like dye chromoendoscopy, but perhaps not clinically significant polyps.
Historically, we couldn’t distinguish between precancerous and non-neoplastic polyps during colonoscopy, so we would remove all of them. With optical chromoendoscopy, because it accentuates the surface patterns of the polyps, there’s now a well characterized classification system to help delineate the polyp from being neoplastic vs. non-neoplastic.
Endoscopists can be trained in this and learn to accurately predict polyp histology in real time. That obviates the need to take out benign polyps, saving the patient the risk of removing the polyp and the time and cost associated with it. It helps us focus on the precancerous polyps and their removal.
Computer-aided programs can also be trained to make these classifications. Recent studies show these computer programs perform just as well as expert endoscopists and, over time, these programs will likely be incorporated into our real-time colonoscopy software. A computer will help us determine if a polyp is precancerous or not and whether we need to remove it. (See page 29 for more details on artificial intelligence in CRC screening.)
We have made incredible advances in the widespread uptake of colon cancer screening and the quality of screening and prevention options we can offer to patients. Nonetheless, CRC remains the second leading cause of cancer-related death in the U.S. We need to focus on reaching the 30% to 35% of Americans over the age of 50 who have not undergone screening and identifying younger patients at increased risk. Once a patient makes it to screening, we are encouraged by evolving techniques and technologies that will continue to enhance the quality of colonoscopy performed by a well-trained and thorough endoscopist.
- For more information:
- Swati Patel, MD, is a member of the ASGE Research Committee and assistant professor of medicine at the University of Colorado. She can be reached at firstname.lastname@example.org.
Disclosure: Patel reports no relevant financial disclosures.