Background Vimentin is a member of the intermediate filament proteins and a canonical marker of the epithelial-mesenchymal transition (EMT), which is pivotal in tumorigenesis, metastasis and invasion in non-small cell lung cancer (NSCLC). The current meta-analysis aimed to investigate the associations between vimentin and prognosis and progression in NSCLC. Methods Databases with literature published in English, including PubMed, Web of Science, Embase, Science Direct, Wiley Online Library, Ovid, Cochrane Central Register of Controlled Trials, LILACS and Google Scholar, and the CNKI, VIP, CBM and WanFang databases in Chinese were used for the literature search. The key terms included (1) 'vimentin' OR 'vim' OR 'vmt' OR 'vm' OR 'hel113' OR 'ctrct30' and (2) 'pulmon*' OR 'lung' OR 'alveolar' and (3) 'cancer' OR 'carcinoma' OR 'tumor' OR 'adenocarcinoma' OR 'squamous' OR 'neoplas*' OR 'malignan*'. The data were combined by random effect model and the H value and I 2 were used to assess the heterogeneity. All the meta-analysis was conducted using Stata 12.0. Results Thirty-two qualified studies (4118 cases) were included in the current meta-analysis. Twelve studies with 1750 patients were included to assess the significance of vimentin in the overall survival (OS) of NSCLC; the pooled hazard ratio (HR) was 1.831 (confidence interval (CI): 1.315-2.550, P<0.001) in the univariate analysis and 1.266 (CI: 0.906-1.768, P = 0.167) in the multivariate analysis. Four studies with 988 cases were applicable to determine the significance of vimentin in the disease-free survival (DFS) of NSCLC; the pooled HR of the DFS was 1.224 (CI: 0.921-1.628, P = 0.164) in the univariate analysis and 1.254 (CI: 0.985-1.956, P = 0.067) in the multivariate analysis. Regarding the relationships between vimentin and clinicopathological factors, the pooled odds ratio (OR) with 3406 NSCLCs indicated that up-regulated vimentin was associated with smoking (OR = 1.359, CI: 1.098-1.683, P = 0.004), poor differentiation (OR = 2.133, CI: 1.664-2.735, P<0.001), an advanced TNM stage (OR = 3.275, CI: 1.987-5.397, P<0.001), vascular invasion (OR = 3.492, CI: 1.063-11.472, P = 0.039), lymph node metastasis (OR = 2.628, CI: 1.857-3.718, P<0.001), recurrence (OR = 1.631, CI: 1.052-2.528, P = 0.029) and pleural invasion (OR = 2.346, CI: 1.397-3.941, P = 0.001). There was no significant correlation between vimentin and age, gender, diameter, T stage, distant metastasis, or marginal invasion (P>0.05). Conclusion An overexpression of vimentin may predict the progression and an unfavorable survival of NSCLC. Vimentin may represent a helpful biomarker and a potential target for the treatment strategies of NSCLC. Additional, prospective studies with large samples are necessary to confirm the significance of vimentin in NSCLC.
