BACKGROUND: The aim of this study was to investigate the expression level of circulating microRNA-31(miRNA-31) in lung cancer patients and its clinical significance.
MATERIAL AND METHODS: Real-time fluorescent quantitative PCR was utilized to detect the circulating miRNA-31 expression levels in 300 lung cancer patients and 300 health control subjects. The ROC curve was drawn to evaluate the diagnostic value of the circulating miRNA-31 expression levels in lung cancer. The 300 lung cancer patients were divided into a miRNA-31 low-expression group and a miRNA-31 high-expression group. A survival curve was drawn according to the Kaplan-Meier method to evaluate the prognostic value of the circulating microRNA-31 expression levels for lung cancer.
RESULTS: The circulating miRNA-31 expression levels in the lung cancer patients (l.88±0. 67) increased significantly (P<0.001) compared to the healthy controls (0.58±0. 44). The area under the ROC curve drawn according to the circulating miRNA-31 expression levels was 0.785 (95% CI=0.486–0.763). When the critical value was 1.27, the sensitivity and specificity for lung cancer diagnosis according to the circulating miRNA-31 expression levels were 0.769 and 0.745, respectively. The difference in the survival curve between the miRNA-31 low-expression group (123 cases) and high-expression group (177 cases) was statistically significant (P=0.004). Median survival period of the low-expression group (38.44 months) was longer than that of the high-expression group (25.23 months).
CONCLUSIONS: miRNA-31 may be a molecular marker for the diagnostic and prognostic evaluation of primary lung cancer.

Keywords: Case-Control Studies, Aged, Gene Expression Regulation, Neoplastic, Humans, Kaplan-Meier Estimate, Lung Neoplasms - surgery, MicroRNAs - genetics, Middle Aged, Postoperative Care, Prognosis, ROC Curve