> The problem with this is that no interval of preventative testing can be rationalized. You don't know if once a decade, or once a year, or using your privilege to get tests every 3 months would yield any help in early detection at all!
Actually, you can study these things and see what it does to outcomes, and professionals have.
There's benefits from more frequent screening (and harms, too!). The benefits are tempered by a cancer manifesting at stage 4 could mean:
* You got unlucky with the screening interval and it showed up inbetween, or
* You have a really aggressive cancer that went from stage 1 to stage 4 in a small fraction of the screening interval.
The latter is interesting: if you are screening at an interval, the later stage cancers you find are, on average, more aggressive and faster growing. In turn, spotting them earlier doesn't necessarily lead to better outcomes.
That is: part of the reason why "finding cancer earlier" is associated with better outcomes is that it's easier to find less aggressive cancers earlier.