Trends of lung cancer incidence by histologic type: A population-based study in Osaka, Japan

We investigated trends of lung cancer incidence from 1973 to 1993 by histol ogic type, using data from the population-based cancer registry in Osaka, J apan. Since the proportion of eases with histologic types identified was no t sufficiently high, sex- and age-specific incidence rates by histologic ty pes were estimated assuming that the distribution of histologic types was t he same across the same ses and age group regardless of reporting status. C umulative risk from 0 to 74 Sears old for total lung cancer increased 1.3-f old from the period 1971-77 to 1986-89 and then plateaued in the period 199 0-93 for both males and females. When divided into histologic types cumulat ive risk for incidence of squamous cell carcinoma was almost constant durin g the study period for both males and females, During the same period, aden ocarcinoma increased up to 1.4-fold for both males and females. This increa se 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 bo th 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 increas e of adenocarcinoma compared to squamous cell carcinoma. Recent trends of t apering increase of lung cancer incidence should he confirmed by further ob servation.