Where are you getting "50% mortality reduction" from? The article says the reduction was zero:
> After 10 years, the researchers found that the participants who were invited to colonoscopy had an 18% reduction in colon cancer risk but were no less likely to die from colon cancer than those who were never invited to screening.
> When the investigators compared just the 42% of participants in the invited group who actually showed up for a colonoscopy to the control group, they saw about a 30% reduction in colon cancer risk and a 50% reduction in colon cancer death
I don’t see how that says much about the usefulness of colonoscopy.
The people in the treatment group who didn’t show up must have had a 36% increase in colon cancer death (not explicitly stated in the article, but can be derived from the numbers. You need 42% × 50% + 58% × ? = 1), and (solving 42% × 70% + 58% × ? = 1) a 21% increase in colon cancer risk.
Something must have made them different from the control group. Maybe, they didn’t show up because they already were being treated for colon cancer?
> After 10 years, the researchers found that the participants who were invited to colonoscopy had an 18% reduction in colon cancer risk but were no less likely to die from colon cancer than those who were never invited to screening.