Several observational studies have suggested that the use of metformin and TZDs is associated with a decreased risk of lung cancer compared with other glucoselowering drugs. In contrast, others have shown a nonsignificant protective effect on lung cancer. Likewise, insulin and insulin secretagogues have been shown to be related to higher lung cancer incidence and cancer-related mortality. But others have shown no harmful or even protective effects. Although there have been some systematic reviews on the relevant subject, some results of previous systematic reviews remain inconsistent. Some other earlier systematic reviews do not MLN4924 citations specialize in lung cancer or are limited by small study sizes. To investigate the relationship between the use of glucoselowering drug and lung cancer risk in patients with diabetes, we conducted a metaanalysis of existing randomised controlled trials and observational studies. Data was extracted from all selected studies by two reviewers working independently, using a standardised form to ensure capture of all relevant information. The following data were collected from each study: first author��s name, publication date, country, study design, time period, mean follow-up time, outcome assessment, type of diabetes, total subjects, lung cancer cases, ratio of each glucose-lowering drug. Where available, adjusted OR or HR values were analysed. If data from any of the above categories were not reported in the primary study, items were treated as ����not available����. For all analyses, the control group was composed of patients with diabetes not exposed to medication of interest. We did not require a minimum number of patients for a study to be included in our meta-analysis. Two reviewers assessed the risk of bias in observational studies according to the Newcastle �C Ottawa Scale which included selection, comparability of studies groups, and ascertainment of exposure or outcome. The overall maximum score was 9 points. The two reviewers applied the Cochrane Collaboration�� s tool to evaluate the risk of bias of randomised trials. This tool based on randomisation, blinding allocation concealment SAR131675 procedures and loss to follow up. Disagreements were resolved by discussion and consensus.