A case‐control study for evaluating lung‐cancer screening in Japan

In order to evaluate the efficacy of lung-cancer screening, a case-control study was conducted using the data from 50 areas where population-based lung-cancer screening programmes have been operated by local municipalities. In most areas, chest X-ray examinations for all participants and sputum cytology for high-risk participants were offered annually. Case series consisted of 273 deceased lung-cancer cases. For each case, 2 to 5 controls (a total of 1,269 controls) were collected from those who were alive at the time of diagnosis of the corresponding case, matched by sex, age, smoking status and type of health insurance. Cases and controls were limited to a high-risk group for males and a non-high-risk group for females. Screening histories, which were obtained from the list of screenees, were compared between case and matched controls for the identical calendar period before the time of diagnosis of the case. The odds ratio of dying from lung cancer for those screened within 12 months vs. those not screened was 0.72 (95% confidence interval 0.50-1.03; p = 0.07). The odds ratio increased towards unity, as the length of time in which screening histories were compared increased. After adjusting for some other variables, which appeared to be associated with the opportunities of chest X-ray examination, the estimated odds ratio did not change. These results suggest some benefits from lung-cancer screening in terms of reduction of lung-cancer mortality and should be subject to further research.