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The contrasting letters by Ben Gray and Peter Zohrab highlight the complexity of allocating limited health resources.1,2 PSA screening for prostate cancer in asymptomatic men promises early and potentially life-saving detection of a serious illness. However, the evidence from trials on benefits versus harms is equivocal, the number needed to treat (screen) is large, and untargeted screening increases the likelihood of harm due to over-diagnosis and over-treatment.3
We note with interest the warning provided by Erik Monasterio of the adverse effects a culture of over-diagnosis and over-treatment may have on patients and health systems generally.4 The effects of over-diagnosis of prostate cancer specifically, and the medicalisation of elevated risk regardless of treatment effects on length or quality of life, have also long been recognised.5
Mr Zohrab calls for more clinical studies to resolve the issue, particularly those which investigate shorter screening intervals and use control arms 'uncontaminated' by men who have had PSA screening outside the trial.2 The lure of 'perfect' data is seductive, but difficult if not impossible to achieve in practice.
Convincing men to accept recruitment to a control arm that prohibits access to an otherwise available test will not be easy. Similarly, researchers proposing to investigate more frequent screening would have to argue that this would not unduly increase risks of harm. As alluded to above, harms from PSA screening may outweigh benefits in a wide range of scenarios.6