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Opinion
Cancer, concepts, cohorts and complexity: avoiding oversimplification of overdiagnosis
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  1. Frank C Detterbeck
  1. Correspondence to Dr Frank C Detterbeck, Yale University School of Medicine, Thoracic Surgery, 330 Cedar St, BB205, New Haven, CT 06520-8062, USA; frank.detterbeck{at}yale.edu

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‘Is cure necessary for those in whom it is possible and possible in those in whom it is necessary?’ Willet Whitman.

Introduction

A cancer diagnosis strikes intense fear in us, and for good reason. Cancer is the leading cause of death in people aged less than 85 years,1 and is viewed as a death sentence which few can escape. Lung cancer is particularly ominous, accounting for more than the next three leading causes combined.

However, the National Lung Screening Trial provides hope, demonstrating 20% less lung cancer deaths through CT screening.2 This study also stimulates a focus on overdiagnosis—meaning, any cancer that would not result in death if left untreated. This concept contrasts starkly with the general view of lung cancer as a rapidly fatal disease. This binary, black-and-white view glosses over nuances and hampers a true understanding. Our conceptual framework profoundly affects our understanding of issues, and our thinking must keep pace with advances in an increasingly complex world. This article explores the concept of overdiagnosis and potential implications of CT screening.

Overview of overdiagnosis

Extensive evidence indicates that overdiagnosis occurs in many cancers3; although difficult to quantify, the proportion is substantial. Autopsy studies, and studies involving resections for non-malignant reasons (eg, prostatic hypertrophy), suggest undiagnosed prostate, thyroid, breast or lung cancers exist in 10–70% of middle-aged and older individuals.3–5 In addition, long-term follow-up of randomised screening studies (allowing for ‘catch-up’ cancers that are diagnosed later in the non-screened arms), suggests that 15–50% of breast and lung cancers represent overdiagnosis in mammography and chest radiograph screening studies.3 ,6 ,7 Probably the strongest evidence comes from population-based studies demonstrating that in many cancers the rate of diagnosis has doubled or tripled, yet the death rate remains unchanged (eg, melanoma, thyroid, renal carcinoma).3 The increased rate …

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