BACKGROUND: We aimed to systematically summarize the diagnostic and prognostic value of circulating/tissue miR21 in patients with colorectal cancer. METHODS: An original study was conducted to explore the potential value of circulating miR21 in colorectal cancer diagnosis and tissue miR21 in colorectal cancer prognosis. PUBMED and EMBASE were searched (to August, 2013) to identify eligible studies. To explore the diagnostic performance of circulating miR21, meta-analysis methods were used to pool sensitivity, specificity, positive and negative likelihood ratio, diagnostic OR and to construct a summary ROC curve. For prognostic meta-analysis, study-specific HRs of tissue miR21 for survival were summarized. Subgroup and sensitivity analyses were applied to explore heterogeneity. RESULTS: Finally, 14 studies (including our study) were included in the meta-analyses. The pooled sensitivity, specificity, and AUC of circulating miR21 were 0.76 [95% confidence interval (CI), 0.59-0.88], 0.81 (95% CI, 0.76-0.85), and 0.81 (95% CI, 0.78-0.85) in diagnosing colorectal cancer. Patients with higher expression of tissue miR21 had significant inferior overall survival (OS; pooled HR, 1.56; 95% CI, 1.16-2.11) and disease-free survival (DFS; pooled HR, 1.35; 95% CI, 1.08-1.69). The individual participant data (IPD) meta-analysis demonstrated that tissue miR21 level was independently associated with worse colorectal cancer OS (HR, 1.69; 95% CI, 1.07-2.67; P = 0.023), whereas this association seems to be confined to males (P = 0.007) but not for females (P = 0.845). CONCLUSIONS: Circulating miR21 level has potential value for colorectal cancer early detection, whereas high tissue miR21 level is associated with adverse colorectal cancer prognosis. IMPACT: miR21 is a promising biomarker for early detection and prognosis of colorectal cancer. Cancer Epidemiol Biomarkers Prev; 23(12); 2783-92. ©2014 AACR.
