Cigarette smoking and lung cancer-relative risk estimates for the major histological types from a pooled analysis of case-control studies

摘要

Lung cancer is mainly caused by smoking, but the quantitative relations between smoking and histologic subtypes of lung cancerremain inconclusive. By using one of the largest lung cancer datasets ever assembled, we explored the impact of smoking onrisks of the major cell types of lung cancer. This pooled analysis included 13,169 cases and 16,010 controls from Europe andCanada. Studies with population controls comprised 66.5% of the subjects. Adenocarcinoma (AdCa) was the most prevalentsubtype in never smokers and in women. Squamous cell carcinoma (SqCC) predominated in male smokers. Age-adjusted oddsratios (ORs) were estimated with logistic regression. ORs were elevated for all metrics of exposure to cigarette smoke and werehigher for SqCC and small cell lung cancer (SCLC) than for AdCa. Current male smokers with an average daily dose of >30cigarettes had ORs of 103.5 (95% confidence interval (CI): 74.8–143.2) for SqCC, 111.3 (95% CI: 69.8–177.5) for SCLC and 21.9(95% CI: 16.6–29.0) for AdCa. In women, the corresponding ORs were 62.7 (95% CI: 31.5–124.6), 108.6 (95% CI: 50.7–232.8)and 16.8 (95% CI: 9.2–30.6), respectively. Although ORs started to decline soon after quitting, they did not fully return to thebaseline risk of never smokers even 35 years after cessation. The major result that smoking exerted a steeper risk gradient onSqCC and SCLC than on AdCa is in line with previous population data and biological understanding of lung cancer development.