Background: There is an urgent need for novel noninvasive prognostic molecular tumor marker for monitoring the recurrence of breast cancer. MicroRNA-21 (miR-21) play a crucial role in the progression and aggressiveness of breast cancer, but its prognostic significance for patients with breast cancer remains inconclusive. The aim of this meta-analysis is to summarize the role of circulating miR-21 as a molecular marker in patients with breast cancer.
Material and methods: Eligible studies were searched from the PubMed, EMBASE and Web of Science databases. The χ2 and I2 tests were used to evaluate heterogeneity between studies. The pooled hazard ratios (HR) with 95% confidence interval (CI) were calculated by a fixed-effects model, if no heterogeneity existed. If there was heterogeneity, a random-effects model was applied. The meta-analysis was conducted using the Review Manager 5 software.
Results: A total of 7 articles which included 1629 cases were selected for the meta-analysis. Elevated miR-21 expression was significantly predictive of poor overall survival (HR = 1.51, 95%CI 1.15-1.98, p = 0.003). The subgroup analysis consisted of in tissue sample (HR = 1.66, 95%CI 1.03-2.67, p = 0.04) and serum sample (HR = 1.73, 95%CI 1.22-2.46, p = 0.002). The association between miR-21 expression level and lymph node metastasis was statistically significant (OR = 2.36, 95%CI 1.04-4.78, p = 0.03).
Conclusion: Our findings suggest that the circulating miR-21 expression level can predict poor prognosis in patients with breast cancer.
Keywords: Circulating miR-21; breast cancer; meta-analysis; prognostic.