Reduction and cessation of cigarette smoking and risk of cancer: a cohort study of Korean men.

PURPOSE: Reducing cigarette smoking has been proposed as a method of harm reduction. The effect of smoking reduction on cancer risk has not been studied in Asian populations.

PATIENTS AND METHODS: A total of 479,156 Korean men, age 30 to 58 years, were stratified into nine groups based on smoking status in 1990 and 1992. From 1992 to 2003, patients were observed and tested for the occurrence of cancer.

RESULTS: There was no association between smoking reduction and risk of all cancers. However, the risk of smoking-related cancers tended to decrease, though not significantly, when heavy smokers (> or = 20 cigarettes/d) became moderate smokers (10 to 19 cigarettes/d), with a hazard ratio (HR) of 0.91 (95% CI, 0.82 to 1.02). For lung cancer, patients who reduced from heavy to moderate smoking and from heavy to light smoking (< 10 cigarettes/d) had significantly decreased risks based on multivariable-adjusted HRs (HR = 0.72, 95% CI, 0.49 to 0.89; HR = 0.63, 95% CI, 0.46 to 0.84, respectively). Study participants who never smoked, sustained ex-smokers, and quitters had lower risks for all cancers, smoking-related cancers, and lung cancer in a dose-response manner as compared with heavy smokers.

CONCLUSION: Smoking reduction was associated with a significant decrease in the risk of lung cancer, but the size of risk reduction was disproportionately smaller than that expected from the reduced amount of cigarette consumption. Although smoking cessation should be the cornerstone of preventing smoking-related cancers, smoking reduction could be considered as a strategy to supplement smoking cessation for those who are unable to quit smoking immediately.