Prognostic value of microRNAs in lung cancer: A systematic review and meta-analysis

Lung cancer is one of the leading causes of cancer-associated mortality throughout the world. The prognosis of the disease depends on many factors including the stage and type of cancer. Many studies have identified various microRNAs (miRNAs) that affect the prognosis of lung cancer. In order to systemically analyze the available clinical data, the present study performed a meta-analysis to examine all evidence on the potential role of miRNAs as novel predictors of survival in lung cancer. Literature published in English prior to February 1st, 2018 was searched through PubMed to review all of the associations between individual miRNAs and groups of miRNAs with the prognosis of lung cancer. Data was extracted using standard forms and pooled odds ratios with 95% confidence intervals (CIs) were calculated. A total of 15 eligible studies were included in the meta-analysis. These represented 1,753 lung cancer patients and 20 miRNAs. A total of 8 downregulated miRNAs were associated with poorer overall survival (OS) [hazard ratio (HR)=0.59, 95% CI: 0.47-0.75, P<1×10^-4], while 10 upregulated miRNAs were associated with poorer OS (HR=1.76, 95% CI: 1.31-2.35, P<1×10^-4). Additionally, low miRNA expression was associated with lymph node metastasis [LNM; relative risk (RR)=0.53, 95% CI: 0.46-0.61, P<1×10^-4]. The expression of miRNAs was not associated with lung cancer stage (RR=1.07, 95% CI: 0.94-1.22, P=0.23). Expression levels of different miRNAs were associated with the OS and LNM of patients with lung cancer. These miRNAs may be applied as potential prognostic markers in lung cancer.