On: Proteins in blood could provide early cancer warning 'by more than seven years'

[vidarh]

Because screening leads to interventions when it is the data used for deciding whether to do an intervention.

If a screening procedure leads only to interventions that would be made in time anyway, it doesn't provide a benefit.

If it leads to extra interventions and no drop in mortality, it may be a net negative.

E.g irradiate enough people to find more cancers and not improve outcomes, and some of your screening may lead to cancers.