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www.medscape.com/viewarticle/863448
COLON CANCER SCREENING HAS PLATEAUED
Hello. I'm Dr David Johnson, professor of medicine and chief of gastroenterology at Eastern Virginia Medical School in Norfolk, Virginia.
We have a new screening test that was recently approved by the US Food and Drug Administration (FDA). Epi proColon (Epigenomics AG) is a blood-based test to screen for colorectal cancer. How do we put this into our armamentarium?
First of all, we know that colon cancer screening has really plateaued. We have a challenge before us because the Centers for Disease Control and Prevention has set a new target that we would achieve 80% screening by 2018. However, what we have seen in the past 5 years is a plateauing effect. When we had momentum with raising awareness of colon cancer screening, and we had people like Katie Couric talking about getting to your doctor and asking about colonoscopy, we got to about 60%, but now we've plateaued. During the past 2-5 years, we haven't made more than about 1%-2% progress in our ability to get more people into the system for screening. We still have about one third of people who don't get adequate screening.
How do we get there? We know that choice makes a difference, and that's very important. As we give our patients a screening discussion, we offer them options. We obviously say that colonoscopy is the preferred strategy. It's the best not only for detection but also for prevention of colon cancer. It's the only prevention test we have because we remove precancerous polyps.
What if a patient says no? There are many reasons for patients to say no, aren't there? You all deal with this in day-to-day interactions with patients.
They don't want to do stool-based testing. We know that the fecal immunohistochemical test (FIT) is better than the fecal occult blood test. Or maybe we don't even want to mess with these new stool DNA tests, which don't require handling stool but nonetheless are stool-based tests. Prep-based tests include CT colonography, colonoscopy, and flexible sigmoidoscopy. A lot of patients don't like the prep, so we still get this plateau effect. How do we get to 80% by 2018?
A NEW, EASIER OPTION FOR COLON CANCER SCREENING
We know that when patients are given options, they will be more compliant. We have to preferentially explain what the science is when we give the options.
Emerging now is a blood-based test for colon cancer screening. We know that blood-based testing is routine for patients when they come into the clinic. When they get screened for their annual physical, they can do a colon cancer screening test if they refused everything else. This is something that patients may be more receptive to.
This new blood test tests for methylation of the SEPT9 gene. There are a number of molecular pathways for colon cancer. We know a lot about this ever since Vogelstein and colleagues[1] at Johns Hopkins University discovered the chromosomal instability pathway. We now know that there are mismatched repair pathways, also known as the Lynch pathways, and those type of syndromic cancers. We also recognize that there is a methylation aberration on DNA that is another molecular pathway.
Something that is very important to understand is that one test doesn't catch all; there are variances. What we want is a test that gets most of the people that we'd miss if they didn't get screened. This new blood test looks for DNA methylation of this SEPT9 gene, which encodes for septin 9. This septin 9 DNA in the serum is discriminate, at least in the tests that have been done for normal vs colon cancer. This pathway is very interesting because the SEPT9 gene encodes for septin 9, a protein that helps regulate normal death of cells. It actually works as a tumor suppressor, regulating orderly and controlled cell growth. It's a very important protein, and if it's aberrant we start to lose those things.
This blood test detects methylation of the SEPT9 gene, and it is easy to do. Compared against fecal tests, the studies[2,3] have shownwhich led to FDA approvalthat it is noninferior to the standard FIT, which is the new test to replace fecal occult blood testing. "Noninferior" means that it did no better, no worse. Sensitivity of detection was around 73%. That's great, but we're talking about colon cancer detection, not polyp detection and prevention of cancer. What a positive test means, then, is that those patients went on to get a colonoscopy. That is the recommendation.
The specificity was a bit different from the FIT. There is a 10%-15% variance on specificity for false positives with this blood-based test. More patients will come back with a negative colonoscopy than would perhaps if you did FIT-based testing, but it's not a bad thing if you drove more people to colonoscopy and they adequately had precancerous lesions picked up.
Interestingly, when they looked at the cancers detected from the septin 9 (SEPT9) methylated DNA test vs FIT, the cancers overlapped in about two thirds of detections, but there were still about one third that were different detections. One is detecting cancers that are only detectable by shedding blood. Hypermethylation might not have that same path or that same expression, so a combination of these tests may be something of value at some point.
WHO ARE THESE TESTS FOR?
Where do I put this test as it relates to screening recommendations?
First, choice is important.
Second, these tests are really best done for patients who have refused other tests. In a study[4] that was done in Germany, they offered the test to patients who were noncompliant with at least two previous recommendations for testing. They were then randomized to receive a recommendation for the methylated septin 9 or the standard FIT. There was about an 11% difference in patients who showed up and had their blood test done versus patients who sent in their stool tests. I think compliance becomes a notable potential variance that we need to pay attention to. Patients are very accustomed to having one blood test done when they are on their way out of the clinic, and it's easy to add in [another].
It's important to recognize that this test is not for patients who are symptomatic, those who have signs or symptoms, or those in whom you suspect that other things are going oncertainly not patients who are at high risk, patients with prior polyps, or patients with familial risks. It is something that is recognized to have an overlap with some other disease states, so a positive test doesn't necessarily reflect cancer, nor does a negative test reflect an absence of cancer. We need to put that into perspective.
We do need to give patients choices. Again, if we're going to get to 80% screened by 2018, we need to put all of these choices out there, understanding that patients are getting a noninferior test that they may be more receptive to taking because it's a standard blood test.
Expand your horizons, understand the tests, and recognize that when patients ask you questions, colonoscopy is still the preferred screening strategy; it's our only cancer prevention test. But, again, we have to accept what patients are willing to do. There is no preparation for this test, with no requirement for avoidance of anything prior to the blood test.
Put it on your menunot at the top of your menu, but at least understand the mechanics of it. Let's get more people screened.
I'm Dr David Johnson. Thanks again for listening.
