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The peer-reviewed journal of the Sax Institute
RESEARCH ARTICLE (Open Access)

What is overdiagnosis and why should we take it seriously in cancer screening?

Stacy Carter A * and Alexandra Barratt A
+ Author Affiliations
- Author Affiliations

A Centre for Values, Ethics and the Law in Medicine, University of Sydney, NSW, Australia

* Correspondence to: stacy.carter@sydney.edu.au

Public Health Research and Practice 27, e2731722 https://doi.org/10.17061/phrp2731722
Published: 26 July 2017

2017 © Carter et al. This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Licence, which allows others to redistribute, adapt and share this work non-commercially provided they attribute the work and any adapted version of it is distributed under the same Creative Commons licence terms.

Abstract

Overdiagnosis occurs in a population when conditions are diagnosed correctly but the diagnosis produces an unfavourable balance between benefits and harms. In cancer screening, overdiagnosed cancers are those that did not need to be found because they would not have produced symptoms or led to premature death. These overdiagnosed cancers can be distinguished from false positives, which occur when an initial screening test suggests that a person is at high risk but follow-up testing shows them to be at normal risk. The cancers most likely to be overdiagnosed through screening are those of the prostate, thyroid, breast and lung. Overdiagnosis in cancer screening arises largely from the paradoxical problem that screening is most likely to find the slow-growing or dormant cancers that are least likely to harm us, and less likely to find the aggressive, fast-growing cancers that cause cancer mortality. This central paradox has become clearer over recent decades. The more overdiagnosis is produced by a screening program, the less likely the program is to serve its ultimate goal of reducing illness and premature death from cancer. Thus, it is vital that health professionals and researchers continue an open, scientific inquiry into the extent and consequences of overdiagnosis, and devise appropriate responses to it.