[Epidemiology of lung cancer--recent topics]

Lung cancer has been increasing markedly in recent years in Japan. It is estimated that the number of lung cancer deaths will exceed that of stomach cancer deaths by around 1995. The reason of the marked increase of lung cancer deaths is not clear, but the following factors may have contributed to the increase of lung cancer in Japan: 1) the increase in accuracy of diagnosis of lung cancer (a decrease in number of overlooked lung cancer cases), 2) an increase in number of aged population (this factor has been considered in the age adjusted mortality rate), 3) an increase in consumption of cigarettes and an increase of other risk factors of lung cancer. A number of studies have been conducted on the relationship between husband's smoking habit and lung cancer in non-smoking wives. The results of these studies implicate the effect of passive smoking on lung cancer, but more studies are needed to confirm the casual relationship. A recent study by Kawajiri et al on the DNA polymorphism of the cytochrome P450IA1 gene in lung cancer cases implicates a variation of the individual susceptibility to lung cancer.