- James Penston, consultant physician
- 1Scunthorpe General Hospital, Scunthorpe DN15 7BH, UK
Cancer screening is a source of much dispute—in the case of breast cancer, arguments have raged for more than a decade.1 One major concern is how the effects are to be measured. Disease specific mortality is used extensively in trials of cancer screening,2 3and as the aim of screening is to reduce deaths from the target disease,2 4 this might seem to be a suitable end point. But the arguments against using disease specific mortality weigh heavily, and all cause mortality is a better measure.
Uncertainties relating to cause of death
Clearly, the accuracy of disease specific mortality depends on correctly identifying the cause of death. However, this is often unreliable,2 and it entails decisions that can introduce biases, either for or against screening.2 3 Claims that bias favouring screening predominates have been disputed.2 4 Nevertheless, one thing is sure: the accuracy of all cause mortality depends solely on the number of deaths identified and …