Hazard Ratio of Smoking on Lung Cancer in Korea According to Histological Type and Gender

Using nationwide cancer incidence data, we examined whether the strength of the association of cigarette smoking with lung cancer risk differs according to major histological type and gender, taking account of other risk factors in the Korean population. The study population derived from government employees and teachers aged 20 years and over who participated in a national health examination program in 1998 or 1999. Total study subjects were 1,357,447. After excluding 1556 subjects who were treated with lung cancer during 1998-2000, we restricted our analysis to 1,355,891 cases. We followed up those 1,355,891 subjects who were cancer-free at baseline until December 31, 2010. The incident cancer cases were identified from the Korea Central Cancer Registry, which is a nationwide hospital-based cancer registry system that includes 94 % of the university hospitals and 96 % of the resident training hospitals of the country. A higher risk for having ever smoked was observed for squamous-cell and small-cell carcinoma in both men and women. Heavy and long-term smokers were at higher risk for these carcinomas. Significant associations with quantity and duration-related factors were observed mainly among men. These findings indicate that smoking is closely related to the risk of squamous-cell and small-cell carcinoma among women as well as men. However, the magnitude of smoking-related lung cancer risk is likely to differ between men and women. The hazard ratios for all types of lung cancer were significantly higher in male current smokers than in male never smokers. In case of women, the hazard ratios for adenocarcinoma were not different between current smokers and never smokers. The hazard ratios we found, however, were lower than those reported in Western countries and in Korea, but consistent with those reported in North-eastern Asian countries.