A screening test’s path to success is thus surprisingly long and narrow. It must avoid the pitfalls of overdiagnosis and underdiagnosis. It must steer past the narrow temptation to use early detection as an end in itself. Then, it must navigate the treacherous straits of bias and selection. “Survival,” seductively simple, cannot be its end point. And adequate randomization at each step is critical. Only a test capable of meeting all these criteria—proving mortality benefit in a genuinely randomized setting with an acceptable over- and underdiagnosis rate—can be judged a success. With the odds
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