Impact of reduced smoking rates on lung cancer screening programs in Japan

In Japan, lung cancer screening by annual chest radiography has been performed for the past 30 years. However, changes in risk factor status may have influenced the efficiency of current organized lung cancer screening program. The purpose of this study was to clarify whether the reduced smoking rate in younger Japanese affects the efficiency and effectiveness of lung cancer screening.

We investigated chronological changes in epidemiological indicators, which support lung cancer screening programs offered by the Japan Cancer Society, such as gender- and age-specific numbers of participants and lung cancers detected by the screening by clinical stage, in relation to smoking rates from 1991 to 2016.

Participant age at the time of screening and age at the time of cancer detection have both increased over time. The lung cancer detection rate (LCDR) in younger age cohorts tended to decrease from 1991 to 2016 in both genders, particularly men aged <55 years. Age-adjusted LCDR significantly decreased from 1991 to 2016 in both genders. After 2001, ~45% of overall detected cases in men and 70% in women were found in stage I. Although trends differed between men and women, smoking rate decreased from 1991 to 2016 in most age cohorts in both genders.

These results suggest that organized lung cancer screening in Japan should be limited to higher-risk populations.