Study objectives: To review the available data on the early detection of lung cancer, with a focus on three technologies: chest x-ray (CXR), sputum cytology, and low-dose CT (LDCT) scanning.
Design, setting, participants: Review of published clinical studies of early detection technologies. The best available evidence on each topic was selected for analysis. Randomized trials were used to evaluate CXR and sputum cytology. Cohort studies, as well as studies providing evidence regarding rates of overdiagnosis and efficacy of initial treatment, were considered in evaluation of LDCT. Study design and results were summarized in evidence tables. Statistical analyses of combined data were not performed.
Measurement and results: Five randomized trials of CXR with or without sputum cytology have been conducted, each which reports disease-specific mortality as well as other end points. None of these studies provide support for the use of either CXR or sputum cytology for the early detection of lung cancer in asymptomatic individuals. Eight completed and ongoing trials of LDCT were identified. All of these studies report the frequency and stage distribution of lung cancers found during initial ("prevalence") screening, and several studies also report rates of detection at the time of annual follow-up. No outcome data on survival or treatment are available. A number of studies support the hypothesis of "overdiagnosis"--that some lung cancers detected by LDCT may behave in an indolent manner.
Conclusions: The use of either CXR or sputum cytology for the early detection of lung cancer is not supported by the published evidence. The evidence for LDCT appears promising, in that the technology typically identifies lung cancer at an early stage, although corollary studies suggest that these findings in isolation may be misleading. Further high-quality research is needed to better define the role of LDCT in the evaluation of asymptomatic high-risk individuals.