The aim of this study was to estimate the effect of exposure to secondhand tobacco smoke on the incidence of lung adenocarcinoma in situ/minimally invasive adenocarcinoma (AIS/ MIA). Data from seven case-control studies participating in the International Lung Cancer Consortium (ILCCO) were pooled, resulting in 625 cases of AIS/MIA and 7, 403 controls, of whom 170 cases and 3, 035 controls were never smokers. Unconditional logistic regression was used to estimate adjusted ORs (ORadj) and 95% confidence intervals (CI), controlling for age, sex, race, smoking status (ever/never), and pack-years of smoking. Study center was included in the models as a randomeffects intercept term. Ever versus never exposure to secondhand tobacco smoke was positively associated with AIS/MIA incidence in all subjects (ORadj = 1.48; 95%CI, 1.14-1.93) and in never smokers (ORadj = 1.45; 95% CI, 1.00-2.12). There was, however, appreciable heterogeneity of ORadj across studies (P = 0.01), and the pooled estimates were largely influenced by one large study (40% of all cases and 30% of all controls). These findings provide weak evidence for an effect of secondhand tobacco smoke exposure on AIS/MIA incidence. Further studies are needed to assess the impact of secondhand tobacco smoke exposure using the newly recommended classification of subtypes of lung adenocarcinoma. Cancer Epidemiol Biomarkers Prev; 24(12); 1902-6.
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