One problem is: how often do those signs turn out to be cancer, versus something else?
There are now circulating tumor cancer DNA tests (ctDNA), though they're presently expensive: https://www.natera.com/oncology/signatera-advanced-cancer-de.... If they get cheap enough, they'd be interesting as part of, say, an annual blood panel. Mine were like $5k each, however, so that's not going to happen in the general population in the short term.
I was using the Signatera tests to try to determine whether I should start prophylactic chemotherapy after a total glossectomy. The answer turned out to be "yes," but three days before I began chemo, a CT scan ordered to ascertain whether I could use a jaw-stretcher device showed six to eight new tumors, less than two months after the surgery. So the direction was correct.