Study objectives: To determine whether intensity, duration, age at initiation, and cessation of cigarette smoking act differently in the development of various histologic types of lung cancer.
Design: A case-control study among deceased men who underwent autopsy, a procedure that involves approximately 73% of all local deaths.
Setting: The Province of Trieste in northeastern Italy
Participants: Seven hundred fifty-five patients with lung cancer, including 267 with squamous cell carcinoma, 218 with small cell carcinoma, 90 with large cell carcinoma, 158 with adenocarcinoma, and 22 with other histologic types, and 755 control subjects who had died of causes other than chronic lung diseases and certain tumors. Information on smoking habits, residential history, and occupational exposure was obtained from each subject's next of kin.
Results: Compared with nonsmokers, the odds ratio (OR) for current smokers was 13.4 for all types combined, 18.8 for squamous cell carcinoma, 14.3 for small cell carcinoma, 34.3 for large cell carcinoma, and 7.9 for adenocarcinoma. Intensity of smoking, duration, age at starting, and dose were all directly associated with all histologic types of lung cancer, although the OR was lower for adenocarcinoma than for other cell types. When results were restricted to ever smokers, exposure-response curves were similar across histologic types. The risk of lung cancer attributable to smoking was 88% for all types combined, 91% for squamous cell carcinoma, 89% for small cell carcinoma, 95% for large cell carcinoma, and 82% for adenocarcinoma.
Conclusions: This study confirms that cigarette smoking causes all types of lung cancer, but the proportion of cases attributable to smoking is lower for adenocarcinoma than for other types, due to a higher proportion of nonsmokers.