[mlyle]

> Sure, but my understanding is that for many types of cancer, detecting that specific cancer early does make a big difference.

The problem is, this is hard to measure. We know that "detected early" correlates with better long term outcomes. But "early" means "smaller and with less spread" which in turn is strongly correlated with "growing slower and spreading less".

We've had unpleasant surprises where e.g. extending screening to earlier ages detects more cancers but doesn't decrease the number of people dying from that type of cancer because of these confounds.