Cancer DNA is detectable in blood years before diagnosis

I actually know a little about this through my work. Cell-free DNA (CfDNA) Has been known about for a few decades, but has become more of a focus in recent years because of the advent of immunotherapies, which are often highly targeted drugs. CfDNA has also been used in "liquid biopsies" i.e, a simple blood draw, because it can help you profile the tumor and location of the cancer.

In my field, we all think that CfDNA testing will eventually become a standard thing that will go along with your annual physical's blood test, because it has predictive/preventative abilities.

how actionable is the result? let's say you do detect trace amounts of tumoral DNA in your blood, what can you do? can you prevent it from developing into a full-on tumor if you don't even know where it is?

I imagine the signature isn't simply binary but with several dimensions of differentiation?