Beware the polyp police

Alan Cassels of British Columbia writes, “The polyp police are coming.”

He explores the introduction of a new Provincial Colon Screening Program in British Columbia. And he raises many questions in a very thoughtful analysis:

“Does a polyp automatically mean a death sentence?

Not at all—only about 2.5 polyps in a thousand will progress to cancer. There is much medical debate around how fast even “precancerous” colonic polyps will go on to develop into full blown cancers; estimates range from 10 to 25 years. Admittedly, finding things that could be precursors to cancer and then leaving them alone is very hard to do. Hunting down and removing polyps seems relatively easy to do and lucrative for those doing it.

But before fully embracing the program, we need to understand the problems colonoscopies themselves can cause both individuals and the health care system.

In the last few years even the most-studied and widely-used screening programs (for breast and prostate cancer, for instance) have faced evidence-based arguments about whether they were doing more harm than good. The main issue has been the possibility of overdiagnosis. In the case of colon cancer, because most of us will have polyps and very few of us will die from them, screening is also liable to result in overdiagnosis and overtreatment.

If and when polyps are found, people may live under a dark cloud, with a “pre-cancerous” label for the rest of their lives. They will certainly be more frequently reminded of their colon health because they will receive many future invitations for follow-up colonoscopies. There is some evidence that depression and suicide is higher among those who submit to screening programs.

From my perspective as a researcher, we need better evaluation of existing screening programs to estimate the benefits; better predictions so we can estimate the burden of the program on the gastronenterology profession; and better information so that people go into screening knowing what to expect—both the potential benefits and potential harm—so they can opt out if they don’t like the odds presented to them. At the end of the day, well-informed citizens, not physicians or the government, should determine if they want to submit to a colon screening program around which there are many questions and unknowns.”

An infographic from the article:

Meantime, this week’s BMJ has a paper, “New polyps, old tricks: controversy about removing benign bowel lesions,” that delivers these key messages:

  • Bowel cancer screening has increased the detection of benign polyps.
  • Not all polyps are equal.
  • Concern about malignancy, which had largely been limited to adenomas, has now been extended to a type of polyp called sessile (flat) serrated polyps.
  • These polyps are less understood than adenomas and more risky to remove.
  • Current consensus guidelines recommend removal of such polyps bigger than 5 mm
  • These guidelines should not be allowed to impair essential research to determine the malignant potential and best management of these polyps.
  • The higher risks associated with their removal may upset the balance of benefit and harm in screening programmes.


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Comments (4)

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Alan Cassels

October 9, 2013 at 11:44 am

The one piece of feedback generated so far from my article was around the statistic “Percent of colon cancers that happen in patients considered ‘average risk’ without a family history of colon cancer: 75%”
I replied to the reader that it is indeed NOT a typo; which is to say three quarters of colon cancers happen in ‘average risk’ people. What I think is happening is that when people consider terms like “high risk” they read into it a death sentence and “average risk” is equated to no risk, when the truth is much more subtle. We need to be better at quantifying risk, so that those labeled at ‘high risk’ don’t have an overblown sense of doom and those considered ‘average risk’ aren’t left thinking they are without any risk whatsoever.

Laurence Alter

October 14, 2013 at 12:24 pm

Dear Mr. Cassells,

Well, count me as an average reader with average understanding of news-writing (reading “The New Yorker” and “The New York Review of Books” doesn’t seem to elevate me much….!). I understand the idea of ‘average’ and, YET, when I read your statistics, I was confused: in your list under “Colonoscopy by the Numbers,” I took the 1st statistic to mean AVERAGE men and AVERAGE women will die from colon cancer in their (average) lives around 3%. I have to assume this implied ‘averageness’ means no special conditions or family inheritance. THEN, I read the 75% statistic for what appears the same group of people.

I should have given up and stopped reading news stories years ago. Kafka makes more sense.


Laurence Alter

Jim Allison

October 15, 2013 at 2:26 am


Congratulations on a well done and informative article. Thanks Gary for highlighting it in healthnews review.

James E. Allison MD, FACP, AGAF
Clinical Professor of Medicine Emeritus UCSF
Division of Gastroenterology UCSF/SFGH
Emeritus Investigator Kaiser Division of Research