The National Cancer Institute's Barry Kramer tackled the issue of over-diagnosis from cancer screening. He explained lead-time bias using an image of Snidely Whiplash tying someone to train tracks. Ineffective screening, he said, is like a pair of binoculars for the person tied to the tracks: you can see the train coming at you sooner, but it doesn't change the moment of impact.
Survival rates after a screening diagnosis increase, even when no one lived a day longer: people have cancer for longer when the diagnosis comes long before any symptoms. Screening is effective, on the other hand, when earlier detection means more people do well than would have done if they'd gone to the doctor first when there were symptoms. Read more in another blog at Scientific American online.
You can get a flavor of the NIH meeting from the tweets under the tag #NIHMiM12.