In patients found to have lung cancer by screening, what is the likelihood that the identified cancer would never have affected that patient?
In patients screened for lung cancer using low-dose computed tomography (LDCT), more than 18% of all lung cancers found are slow-growing and will not cause symptoms or harm during an average 6.4 years of follow-up. This risk of overdiagnosis should be part of the discussion regarding whether to screen. (Level of Evidence = 1b)
Early detection of disease via screening usually makes sense, unless that earlier detection leads to identification of a disease that is never destined to cause problems in the patient. We cannot pinpoint which patients are overdiagnosed; all we can do is understand the concept that some patients will be identified and treated for a disease that would never have become clinically apparent. This study is an analysis of the previously reported National Lung Screening Trial using extended follow-up data. This study enrolled 53,452 patients at high risk of lung cancer (i.e., those between 55 and 74 years of age with at least a 30 pack-year history of smoking). Patients were randomized to receive three annual screens with LDCT or single-view posterior-anterior chest radiography. Patients were followed up for an average of 6.4 years. More lung cancers were reported in the LDCT arm of the study (1,089) than in the chest radiography arm (969). The excess number of cancers in the LDCT arm (18.5%; 95% confidence interval, 5.4% to 30.6%) represents the total number of cancers that would not have become clinically apparent during the screening period had screening not been performed. Most (78.9%) of the bronchioalveolar lung cancers found were an overdiagnosis, and 22.5% of non–small cell lung cancers found were an overdiagnosis.
Study design: Randomized controlled trial (nonblinded)
Funding source: Government
Setting: Outpatient (any)
Reference: PatzEFJrPinskyPGatsonisCet alNLST Overdiagnosis Manuscript Writing Team. Overdiagnosis in low-dose computed tomography screening for lung cancer. JAMA Intern Med.2014; 174( 2): 269– 274.