If I understand right, one of the problems in the case of cancer is that we don't have great data about the people without symptoms who wider screening would ca

If I understand right, one of the problems in the case of cancer is that we don't have great data about the people without symptoms who wider screening would catch. Once we catch them, we treat them, and many recover. But to say how many of those would have been fine anyway, we'd have to know more about the un-screened rest of the population. The hope with widespread cheap screening would be that it might avoid this. If heart-rate smartwatches become as common as smartphones, we could train our treatment model on everyone, and do better. Or at least this sounds mathematically plausible to me (not an expert). Whether it will come to pass, or whether doctors will continue to treat as now (anything which an eyeball test says looks like an early stage of a known disease) I don't know.