Association of Oral Contraceptives Use and Lung Cancer Risk among Women: an Updated Meta-analysis Based on Cohort and Case-control Studies

Background: Previous studies on the association of oral contraceptives (OC) use and lung cancer generatedinconsistent findings. The aim of this study was to confirm any definite correlation between OC use and lungcancer risk.
Methods: Publications were reviewed and obtained through PubMed and EMBASE databasesliterature search up to November, 2013. Reference lists from retrieved articles were also reviewed. The languageof publication was restricted to English. A meta-analysis was performed to evaluate the association by calculatingpooled odds ratios (ORs) and 95% confidence intervals (CIs).
Results: A total of 14 studies consisting of 9 casecontrolstudies and 5 cohort studies were finally included in this meta-analysis. There was no significant associationobserved between OC use and lung cancer risk in the overall analysis (OR=0.91; 95% CI=0.81-1.03). There wasa significant protective effect in Europe (OR=0.74; 95% CI=0.60-0.91) and a borderline significant protectiveeffect with an adenocarcinoma histology (OR=0.90; 95% CI=0.80-1.01) in subgroup analyses. No associationwas observed for methodological quality of study, study design, smoking status and case number of study.
Conclusion: This meta-analysis suggests that OC use is not likely to be associated with the risk of lung cancer atall. While a significant protective effect of OC use on lung cancer was observed in Europe, interpretation shouldbe cautious because of the potential biases of low-quality studies. At the same time, more attention should bepaid to the possible association of OC use with adenocarcinoma of lung. Our findings require further research,with well-conducted and large-scale epidemiological studies to confirm effects of OC use on lung cancer.