[Tobacco smoking and cancer risk: epidemiological evidence]

The positive association between tobacco smoking and the risk of various sites of cancer has been consistently observed in a large number of epidemiological studies in which chance, bias and confounding could be ruled out with reasonable confidence. The relative risk of developing any cancer among smokers is estimated to be 1.6-2.0 in men and 1.3-1.6 in women based on a meta- and pooled-analysis of Japanese studies. More than 29% of total cancer in Japan is estimated to be attributed to tobacco smoking in men while 4% in women. Environmental tobacco smoke, namely passive smoking, is also a cause of lung cancer without any scientific controversy. The relative risk of nonsmoking women with smoking husbands to without is estimated to be approximately 1.3 based on evidence from cohort studies in Japan and a meta-analysis of world-wide epidemiological studies. Tobacco control is the most important and effective strategy for primary prevention of cancer.