Yup this is what needs to be tested, in other words can cancers be detected early enough so that people are more likely to be cured with treatment. Secondary benefits of detecting early are needing less extensive surgery, less intensive chemotherapy and radiation, less expensive next generation therapies in the long run.
We should also remember that the assays are improving all the time.
Having said all this, early detection is not prevention, and the endgame still remains prevention I think.
This whole field also serves as further confirmation that everything intestesting was discovered in the life sciences in the 1970s .