A statistical study of lung cancer in the annual of pathological autopsy cases in Japan, from 1958 to 1997, with reference to time trends of lung cancer in the world.

Lung cancer cases (66650 males and 20890 females) registered in the Annual of Pathological Autopsy Cases in Japan, between 1958 and 1997, were analyzed with regard to sex, age and histology. They were subdivided into decades (periods I to IV), and compared with the Japanese mortality statistics, with which they were in good correspondence. Although the autopsy rate is decreasing, more than 10% of the total lung cancer deaths in Japan were registered by 1990. Among autopsied cases, the incidence of lung cancer cases increased from 6% to 12% in males and from 3% to 6% in females. From period III, lung cancer in males became the most frequent, and was the second most frequent cancer in females after gastric cancer. As for the histological distribution, adenocarcinoma was the most frequent and squamous cell carcinoma was the next most frequent in both sexes. Recently, a significant increase in adenocarcinoma and a significant decrease in squamous cell carcinoma have been observed in both sexes. The peak ages shifted from the 60s to the 70s and a significant rise in the mean ages were observed. The male-to-female ratios and the ratio curves by histological and age group were high for squamous cell carcinoma and small cell carcinoma, while they were low for the total and adenocarcinoma. With the recently acquired data on lung cancer in Asian countries, and from the male-to-female ratios and the status of smoking rates, lung cancer in the world at present was divided into three groups; North America, Europe and Asia. The possibility of one group changing to resemble another and of groups converging in the near future is suggested.