956Cumulative low-tar exposure was still associated with increased lung cancer risk from Japanese case-control study

Background Tar concentration in cigarette brands is chronologically decreasing in the USA and Japan. However, studies investigating lung cancer risk with cumulative tar exposure in Western and Asian countries are insufficient. To investigate the risk of lung cancer with cumulative cigarette tar exposure, we conducted a case-control study among Japanese current smokers. Methods This study used data from the US-Japan lung cancer joint study in 1993–1998. The number of the subjects was 282 histologically confirmed lung cancer cases and 162 hospital and 227 community controls, and two control groups were combined. The information regarding tar concentration was obtained from the published documents and additional estimation using the equation of regression. Cumulative tar concentration was calculated by multiplying the annual value of tar concentration by year and brand. The odds ratios (ORs) and 95% confidence intervals for lung cancer with cumulative tar exposure were estimated using a logistic model. Results The OR with cumulative tar exposure was higher in higher exposed smokers (>45.6 × 105mg, 8.10, 4.74–13.7) than in lower exposed smokers (≤45.6 × 105mg, 3.37, 1.92–5.92), and increasing trend of the ORs was significant (p < 0.001). The stratification analysis showed higher ORs among those with higher cumulative tar exposure regardless of inhalation, duration of smoking filtered cigarettes, and histological type. Conclusions This study showed that cumulative tar exposure is a dose-dependent indicator for lung cancer risk, and low-tar exposure was still associated with increased cancer risk. Key messages Low-tar tobacco is still associated with increased lung cancer risk.