Is Colorectal Cancer on the Run?

David J. Kerr, CBE, MD, DSc, FRCP, FMedSci


May 24, 2016

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Hello. I am David Kerr, professor of cancer medicine from University of Oxford. I would like to talk a little about a recent report that appeared in the New England Journal of Medicine, written by Welch and Robertson.[1] The title is "Colorectal Cancer on the Decline—Why Screening Can't Explain It All."

First, the unambiguous good news. Let's shout it from the rooftops. Since 1975, in the United States, in citizens aged 50 and over, the incidence of colorectal cancer has dropped by 40% and mortality rates have dropped by half. Isn't that fantastic?

The usual buzz in the street is that this is because of screening, that it's made the definitive difference in improving the nation's health in terms of colorectal cancer. But the authors argue, and I think reasonably and rationally, that we cannot pin all of these improvements solely on screening. The authors make a good argument that the delay between introduction of screening and improved mortality is about a decade. They look at the relatively slow uptake of screening throughout the United States; across the population it took a couple of decades for screening uptake to get to reasonable figures.

They cite additional reasons why they think we have seen this remarkable heartwarming improvement in colorectal cancer health. One is better treatment—better surgery, better imaging, better radiotherapy, and the use of adjuvant chemotherapy for node-positive disease. Even with metastatic disease, a quarter of patients are now surviving 5 years or longer using much more aggressive management of the hepatic and pulmonary metastasis. Treatments have improved, and I'm glad that we've contributed to that in some way.

Second, there is better access to screening tools, with increased use of sigmoidoscopy and endoscopy generally. With citizens being more aware of the symptoms and signs of colorectal cancer, there's probably a greater uptake, more use of endoscopy, earlier detection of polyps, and hence the reduction in incidence and mortality.

Third, it does look as though the number of cases has gone down, again before screening really "bit." Probably, improved diet [had an effect], including eating less smoked beef and smoked ham, and a better diet generally. It may be that more widespread use of antibiotics has changed the gut flora. We've seen this with Helicobacter, for example, and there's a huge interest just now in the microbiome of the gut and its association with colorectal cancer.[2,3] There may have been subtle changes in the lower GI flora over the past decade that have could have contributed.

We've talked many times about aspirin as a chemopreventive and other nonsteroidal anti-inflammatory drugs, which are much more widespread than they used to be and therefore would have contributed too. It is an interesting thesis. Of course, screening has had an important impact. We know that in meta-analysis it can reduce both the incidence and mortality from colorectal cancer.[4] Screening has a really important role to play but it doesn't explain everything.

So, there we have an integrated concerted effort in the therapeutic sense, in the public health sense, and perhaps citizens just adopting gradually a generally better lifestyle— improving diet, perhaps a bit more exercise. It's good news, so as I said before, let's shout it from the rooftops that it looks as if—slowly, incrementally, gradually—we've got colorectal cancer on the run.

Thanks for listening, as always. Medscapers, over and out.


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