This would require a test that is (a) cheap (so that it can be applied to basically everyone) and (b) has extremely low false positive ratio (because a particul

This would require a test that is (a) cheap (so that it can be applied to basically everyone) and (b) has extremely low false positive ratio (because a particular kind of cancer is a rare thing). Repeat for every different kind of cancer. For these reasons I'm not sure that it'll end up being a lower hanging fruit than vastly better treatment of late detected cancer for the kinds that are usually detected very late now.