Can American doctors say "No" to an aggressive and high-tech treatment they're used to providing even when it turns out a less heroic and cheaper one works just as well? It's an important question. The affordability of American medical care in the future will depend, in part, on the ability of physicians to simplify and economize, which are two things they've never been good at. With national health expenditures amounting to $2.6 trillion a year—45 percent of it paid by government—prosperity and political stability may also be at stake.