• Lung Cancer

The issue of overdiagnosis is frequently raised in the context of lung cancer screening. Two recent papers draw attention to this matter: one by Patz et al,1 which estimates the incidence of overdiagnosis in the experience of the National Lung Screening Trial, and the US Preventative Services Task Force report that recommends screening in an organised programme for individuals at an elevated risk of developing lung cancer.2 Make everything as simple as possible, but not simpler (Albert Einstein)

Overdiagnosis—what is it exactly? There are many definitions. In the Patz paper these are excess cancers identified in the screening arm of a randomised trial (either in general or among only screen-detected cancers). These excess cancers remain asymptomatic, by definition, since they would otherwise be detected in the non-screening arm during a follow-up phase (‘catch-up period’)—the duration of which is important. A more abstract definition is any excess cancer detected by screening that would not cause death if untreated, whether it becomes symptomatic or not. Others define it as cancer with a long volume doubling time (>400 days) during a period of observation, without addressing what might happen later.3 An existential view considers any cancer as overdiagnosed if the patient dies of other causes, regardless …