Interestingly enough, the effectiveness of colonoscopy has never been evaluated using a gold-standard clinical trial wherein one group (treatment) is evaluated for colon cancer with a colonoscopy and a comparison (control) group is not. This week, the New England Journal of Medicine published results from a “pragmatic” clinical trial wherein over 84,000 men and women between the ages of 55 and 64 years of age from Poland, Norway, Sweden and the Netherlands were split (1:2 ratio) between being “invited” to have a colonoscopy versus “usual care” (no colonoscopy or screening offered).  The study recruited patients between 2009 and 2014, and followed them for up to 10 years (Bretthauer et al.  Link: https://www.nejm.org/doi/full/10.1056/NEJMoa2208375). 

The study found a risk of colon cancer at 10 years to be 0.98% in the invited group versus 1.20% in the usual care group. Mortality rates were 0.28% in the invited group versus 0.31% in the usual care group. 

So at face value, colonoscopy seems to be a pretty underwhelming screening tool – but a couple of caveats:

1. The invited study population was between 55 and 64. Current US recommendations are for colonoscopy to begin at age 45. Earlier screening, in general, has more robust benefits rather than later screening so the older age cohort is a limitation of this study.
2. Colon cancer itself, generally speaking and exclusive of more aggressive cases, can take many years to progress from polyp to cancer may be greater than the 10 years of follow-up undertaken by this current study. So a longer study period would be preferable.
3. Of those study participants invited to have a colonoscopy (total of 28,220 individuals) only 42% (11,483) underwent the procedure. This is a significantly lower percentage of colonoscopy uptake than is typically seen in the US where about 70% of those who are offered colonoscopy then have one.

So overall a very interesting study and even when analyzed with ‘intent to treat’ (i.e. considering all 28.220 as having had a colonoscopy even though only 11,483 did), there was an 18% risk reduction effect associated with the procedure. In short:

“I don’t think this should change our practice,” said Dr. Robin Mendelsohn, a gastroenterologist at Memorial Sloan Kettering Cancer Center in New York City. “The bottom line is still get screened, still have the discussions” with your doctor.