The efficacy of lung cancer screening in Miyagi Prefecture, Japan: A comparison of 2 case-control studies conducted in the 1980s and in the 1990s

Objective: To evaluate the efficacy of lung cancer screening. Methods: In Miyagi Prefecture, Japan, 2 case-control studies to evaluate the efficacy of lung cancer screening were conducted independently in 1988-90 and in 1997-99. We compared the differences in the methods and the results between the two studies. Results: The smoking-adjusted odds ratios were 0.55 in the 1980s (62 cases and 285 controls) and 0.54 in the 1990s (328 cases and 1886 controls), respectively. After excluding sets from the 1990s-study to imitate the conditions of the 1980s-study, the odds ratio of dying from lung cancer in the 1990s changed to 0.27-0.46. Conclusion: The mass screening program for lung cancer reduced the risk for lung cancer death in both case-control studies. The self-selection bias and/or the improvement of diagnostic/therapeutic modality for lung cancer might influence the results in the two studies.