Epidemiological characteristics of adenocarcinoma of the lung in Los Angeles County.

The descriptive epidemiology of adenocarcinoma of the lung was compared with that of squamous cell carcinoma with the use of data for 1972-76 from the population-based cancer registry serving Los Angeles County. Several differences in the demographic characteristics between these two types of lung cancer were observed, including low male-to-female ratios and lack of social class gradients for adenocarcinoma. Cigarette smoking was responsible for 90% of squamous cell carcinoma in both men and women and for 79% of male and 46% of female adenocarcinoma. We also studied incidence rates of lung cancer after subtraction of the proportion of the incidence due to smoking by using data from a previously conducted case-control study in Los Angeles County. These residual rates for squamous cell carcinoma showed a fivefold excess in males compared with females, whereas those for adenocarcinoma were almost the same in men and women. These findings indicate that 1) smoking is etiologically less important for adenocarcinoma than for squamous cell carcinoma, and 2) other etiologic factors for adenocarcinoma affect women as much as men.