UNSURPRISING:

The Nordic-European Initiative on Colorectal Cancer (NordICC) is a huge randomized trial aimed at rigorously measuring how much colonoscopies reduce cancer and death.1

Here's what the researchers did: Between 2009 and 2014, they identified 85,1792 subjects mostly in Poland (64.1%), Norway (31.2%), and Sweden (4.3%), drawn at random from population registries of people between 55 and 64 years old.3 They invited one-third of them to a one-time screening colonoscopy. Of those contacted, 42% accepted the invitation and underwent a colonoscopy, while 58% refused the invitation. The other two-thirds of people were not contacted and seemingly never knew they were in the trial. The researchers then followed everyone (invited or not, colonoscopy or not) for a median of 10 years and checked government records to see who had been diagnosed with colorectal cancer, died from colorectal cancer, or died from any cause. [...]

The 18% reduction in colorectal cancer incidence was statistically significant, while the 10% reduction in colorectal cancer mortality and 1% reduction in overall mortality were not.

So the reductions -- they are small. This was a surprise.

The study had a huge sample and simple, reliable statistics. The authors seemed to expect a stronger showing for colonoscopies. When that didn't happen, they made no excuses -- they just followed their preregistered statistical plan and published the results. We want research to be reproducible, right? Well, then this is what we want people to do.

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