The National Lung Cancer Screening Trial (NLST) demonstrated a mortality reduction benefit associated with low-dose computed tomography (LDCT) screening for lung cancer. There has been considerable debate regarding the benefits and harms of LDCT lung cancer screening, including the challenges related to its practical implementation. One of the controversies regards overdiagnosis, which conceptually denotes diagnosing a cancer that, either because of its indolent, low-aggressiveness biologic behavior or because of limited life expectancy, is unlikely to result in significant morbidity during the patient’s remainder lifetime. In theory, diagnosing and treating these cancers offer no measurable benefit while incurring costs and risks. Therefore, if a screening test detects a substantial number of overdiagnosed cancers, it is less likely to be effective. It has been argued that LDCT screening for lung cancer results in an unacceptably high rate of overdiagnosis. This article aims to defend the opposite stance. Overdiagnosis does exist and to a certain extent is inherent to any cancer-screening test. Nonetheless, the concept is less dualistic and more nuanced than it has been suggested. Furthermore, the average estimates of overdiagnosis in LDCT lung cancer screening based on the totality of published data are likely much lower than the highest published estimates, if a careful definition of a positive screening test reflecting our current understanding of lung cancer biology is utilized. This article presents evidence on why reports of overdiagnosis in lung cancer screening have been exaggerated.
Highlights
LDCT has been proven to decrease lung cancer–specific mortality by 20%, primarily by causing a stage shift at diagnosis from advanced stage noncurable lung cancers to early-stage potentially curable lung cancers.
The most important harms of LDCT screening are the high rate of false positives (which may lead to harm from invasive procedures or unnecessary additional tests) and overdiagnosis (which may lead to treatment of cancers that would not lead to death and morbidity during the patient’s life expectancy).
The main economic limitation for implementation of LDCT screening is cost effectiveness, a metric that is very sensitive to both number of false positives and overdiagnosed cancers.
The scientific literature estimates of overdiagnosis in LDCT screening vary widely, from 2%–3% to 18%–19%, depending on different models and assumptions. Nonetheless, some degree of overdiagnosis is inherent to any screening strategy.
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Why lung cancer screening matters? The clinical challenge
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Lung cancer is a heterogeneous disease: insights from cancer biology
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Lung cancer screening trials and results: benefits of lung cancer screening
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Harms and limitations of lung cancer screening
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Harms: false positives
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Limitations: cost-effectiveness and financial costs
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Harms: overdiagnosis and overtreatment
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Conclusions
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