Metformin does not alter the risk of lung cancer: A case-control analysis

Background: Metformin use has been linked to a decreased cancer risk. We explored the association between use of metformin or other antidiabetic drugs and the risk of lung cancer. Methods: We assessed the association between metformin, and other antidiabetic drugs and lung cancer using a case-control analysis in the UK-based General Practice Research Database (GPRD). Cases were people with an incident diagnosis of lung cancer. Up to 6 controls per case were matched on age, sex, calendar time, general practice, and number of years of active history in the GPRD. The contribution of potential confounders including tuberculosis, chronic obstructive pulmonary disease (COPD), diabetes mellitus, and co-morbid conditions to diabetes was evaluated in univariate models, and final results were adjusted for BMI and smoking. Results: Long-term use (>= 40 prescriptions) of metformin was not associated with an altered risk of lung cancer (adj. OR 1.21, 95% CI 0.97-1.50. Long-term use of sulfonylureas was linked to a marginally decreased risk of lung cancer (adj. OR 0.74, 95% CI 0.60-0.90. This risk decrease was observed in men (adj. OR 0.64,95% CI 0.50-0.83) but not in women (adj. OR 0.97, 95% CI 0.69-1.37) and this risk decrease was not statistically significant in an analysis restricted to diabetic patients only (adj. OR. 0.82, 95% CI 0.65-1.02). Long-term use of insulin was associated with a slightly increased risk of lung cancer (adj. OR 1.33, 95% CI 1.04-1.71); however, no consistent trend across duration strata was observed. Conclusion: Metformin did not decrease the risk of lung cancer. (C) 2012 Elsevier Ireland Ltd. All rights reserved.