Why cancer screening has never been shown to “save lives”—and what we can do about it

Prasad accepts that all-cause mortality is an insensitive outcome in the assessment of the efficacy and harm arising from medical screening programmes, but says it is necessary. The use of insensitive and uninformative endpoints in clinical trials is bad science. It would delay and possibly prevent effective programmes from being adopted (and prolong trials of ineffective interventions). Disease specific outcomes need to be examined.

All-cause mortality will generally be dominated by causes of death that are unrelated to the screening and any intervention that follows, so that any benefit (or harm) from screening will be concealed. This is not to say that a direct assessment of all-cause mortality should be ignored. It may indicate possible benefit or harm but failure to reveal either does not exclude the existence of clear and sufficient evidence of benefit or harm. It is the insensitivity (and lack of specificity) of all-cause mortality as an outcome that is the problem, not the outcome itself.