The argument also goes that some cancers may never become clinically relevant, or in the case of the sick, vulnerable or elderly other causes of death will get you before the cancer does - And so detection in these cases may cause “unnecessary” treatment, patient worry and burden on society.
1. What is the average number of cancers per person as a function of age?
2. How many of those cancers are clinically relevant now?
3. How many will become clinically relevant in the future?
Then we can have an informed discussion about the trade-offs.
Unfortunately, I suspect that nobody actually knows those numbers. (So maybe we have to start doing the scanning, at least on a study population, in order to find out...)
I've experienced this personally, and visibly. I've had a few moles appear on my skin, then subsequently a white ring would appear around it (presumably my body was killing ALL melanocytes in that region?) while the mole slowly shrank over the span of a few months. I have a few dozen other moles that my body never bothered doing anything about.
And this is just the skin. I'm not sure I want to know what's gone on in the other 90% of my biomass.