A lot of cancers have no symptoms at the beginning, but they can be flagged in blood tests performed as part of general health checkups.
I think the optimal move might be regular (possibly more than annual) blood work and only talking to a doctor when there's symptoms.
And if the results look dramatic, get a second or third opinion (and check) before doing anything.
Do annual checkups involve blood tests where you are? I've only had blood taken as part of one once, and that was in direct response to a new diagnosis of a health condition in a grandparent.
Mine do, yes. Kaiser in Northern California region.
Of course, blood and urine. I do them every six months, even though my insurance only covers once a year, I'm happy to pay out of pocket for the second.