COMMENTARY

Don't 'Go Backwards' on Colorectal Cancer Screening

David A. Johnson, MD

Disclosures

October 21, 2019

This transcript has been edited for clarity.

Hello. I'm Dr David Johnson, professor of medicine and chief of gastroenterology at Eastern Virginia Medical School in Norfolk, Virginia.

A recently published clinical practice guideline in the BMJ[1] was received as something of a newsflash, concluding that we shouldn't be performing colon cancer screening for all patients, and absolutely not in some. But is this really news? I can't believe that we shouldn't be doing colon cancer screening.

To better understand this, let's take a closer look at what this guideline showed.

How the New Guidelines Made Their Case

The investigators analyzed four different screening methods: the fecal immunochemical test (FIT) done annually or biannually, and sigmoidoscopy or colonoscopy performed as a one-time test.

The premise was based on new information from three major trials[2,3,4] assessing the screening effectiveness of sigmoidoscopy with up to 15 years of follow-up, two of which suggested a modest decrease in colorectal cancer mortality and incidence with sigmoidoscopy screening in men but no reduction in women.

This group of experts then applied a very innovative tool called QCancer, which was developed specifically for the United Kingdom and predicts the risk for a variety of cancers, including colorectal cancer. Although this tool is only validated for predicting cancer risk over a 10-year window, the authors took the latitude here of extending it to 15 years, based on the sigmoidoscopy data. In doing so, they determined that if you had a 3% or less chance of developing cancer in 15 years, you should not be offered colon cancer screening. If the risk was greater than 3%, the authors suggested that those between the ages of 50 and 79 years should be offered one of these screening options (ie, FIT, sigmoidoscopy, colonoscopy) over the course of 15 years.

QCancer is a tool that involves a number of demographic factors, including age, health history (eg, diabetes, obesity), family history, smoking, and alcohol use. This information is ideally meant to be plugged in with the healthcare provider, after which the risk is calculated to decide whether you need colon cancer screening. The recommendation that otherwise healthy individuals with a 3% or less risk should not be offered screening was described by the authors as being "weak."

A Critical View

Does this mean that we should not use all of the recognized colon cancer screening modalities that we currently have? Should we now score our patients and not screen those who have a 3% or less chance of developing colon cancer in 15 years?

I recommend that before we get too far into the weeds, let's look at some of the issues here.

Because QCancer is developed specifically for the United Kingdom, the demographic inputs related to ethnicity do not include a category for African Americans. That's important to note, because in the United States we've recognized that African Americans develop colon cancer earlier and in a much more aggressive form. The US Multi-Society Task Force [on Colorectal Cancer][5] and the American College of Physicians[6] have agreed that 45 should be the average age to initiate screening for African Americans.

I also took a closer look at the QCancer tool, plugging in demographic information for a Caucasian man of my age, body mass index, and no other health risks, and I found that men would not qualify for screening until they were approximately 62; for women, it was closer to 67. Again, these are solely for Caucasian patients, as African Americans were not included.

We need to back up and remember that we're talking about a relative risk of 3% in the next 15 years for a potentially preventable cancer.

What we have seen in the past two decades in the United States is a progressive decline in colon cancer and related mortality. The overall numbers of colorectal cancer have changed dramatically, because there has also been an increase in the overall population during that time. Nonetheless, we still must recognize that it is the second leading cancer-related death in the United States and in Europe as well.

And although we have made tremendous strides in decreasing the incidence of colon cancer via screening, it has not been enough, because we are not getting sufficient numbers of people in for screening. In fact, in 2015 the Centers for Disease Control and Prevention, with the National Colorectal Cancer Roundtable, put forth a challenge to get the colon cancer screening numbers up from approximately 60% to 80% by 2018.[7] They estimated that if we could do this, by 2030 we would decrease the incidence of colorectal cancer by around 22%, which would equate to 277,000 new cancers prevented; and decrease cancer-related mortality by 33%, which would equate to 203,000 averted deaths.

Let's apply some practical sense here. We cannot use a calculator that doesn't even apply to the United States and doesn't include African Americans. Also, on closer inspection, I noted that when validating this instrument, the sensitivity thresholds for the top 10% at greatest risk were around 50% for males and 46% for females. Although it was better for specificity for cancer prediction—in excess of 90%—we're simply not talking about a very sensitive predictor. Things are not quite so easy as these results would have us believe.

I do applaud the authors for looking for ways to better stratify patients to get the best bang for our buck. Clearly, as we get into genomic sequencing, I think the technology may help better predict who are the best candidates to be screened and screened more intensively.

But for the present day, the train should stay on the tracks, not be headed off of them. And it should be moving forward at a faster pace, getting more people into screening and emphasizing quality colonoscopy, colonoscopists, and polypectomy. It's all about doing the right thing, not getting potentially derailed by a newsflash that suggests that maybe we should do less screening.

Let's not go backwards. Let's put the pedal to the metal.

I'm Dr David Johnson. Thanks again for listening.

David A. Johnson, MD, is professor of medicine and chief of gastroenterology at Eastern Virginia Medical School in Norfolk, Virginia, and a past president of the American College of Gastroenterology. His primary focus is the clinical practice of gastroenterology. He has published extensively in the internal medicine/gastroenterology literature, with principal research interests in esophageal and colon disease, and more recently in sleep and microbiome effects on gastrointestinal health and disease.

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