Trends of Lung Cancer Incidence by Histologic Type: A Population‐based Study in Osaka, Japan

Abstract

We investigated trends of lung cancer incidence from 1974 to 1993 by histologic type, using data from the population-based cancer registry in Osaka, Japan. Since the proportion of cases with histologic types identified was not sufficiently high, sex-and age-specific incidence rates by histologic types were estimated assuming that the distribution of histologic types was the same across the same sex and age group regardless of reporting status. Cumulative risk from 0 to 74 years old for total lung cancer increased 1.3-fold from the period 1974-77 to 1986-89 and then plateaued in the period 1990-93 for both males and females. When divided into histologic types, cumulative risk for incidence of squamous cell carcinoma was almost constant during the study period for both males and females. During the same period, adenocarcinoma increased up to 1.4-fold for both males and females. This increase seemed to have reached a plateau recently for males, but not for females. Small cell carcinoma increased monotonously up to 1.6-to 1.7-fold for both males and females. Large cell carcinoma showed over 2-fold increase for both males and females; however, the estimates fluctuated due to the small number of cases. This study provides further evidence of a relative increase of adenocarcinoma compared to squamous cell carcinoma. Recent trends of tapering increase of lung cancer incidence should be confirmed by further observation.Key words: Lung cancer -Histologic type -Incidence -Trend -Smoking Recent trends of lung cancer incidence are showing different patterns by country. 1) In the US and UK, where lung cancer incidences were relatively high and smoking control has been successfully implemented, incidence of lung cancer in males has reached a peak and now is in the decreasing phase, starting from younger age groups. In contrast, in Eastern Europe, where smoking control has been less successful, the incidence is still increasing. These trends have been greatly influenced by the trends of smoking prevalence. It is well known that the magnitude of association between lung cancer and cigarette smoking differs by histologic types. Squamous cell carcinoma and small cell carcinoma show a 10-to 20-fold increase among current smokers compared to non-smokers, while adenocarcinoma shows a 2-to 5-fold increase.2) Therefore, smoking prevalence influences the trends of incidences differently among histologic types.In the US and Europe, several hospital-based studies, [3][4][5][6] autopsy series 7) and population-based studies [8][9][10][11][12][13][14][15][16] have examined the trends of lung cancer incidence by histologic type. In Asian countries there have been hospitalbased studies, [17][18][19][20] and a population-based study. 21) Most of the studies showed a relative increase of adenocarcinoma as compared to squamous cell carcinoma in both males and females, especially in younger age groups. Lung cancer incidence in Japan has been relatively low compared to other countries. It is reported that cumulative risk (0-74 years old) of lung c...

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