The expression of miR-21 and miR-375 predict prognosis of esophageal cancer

Twenty-two studies including a total of 1946 participants were enrolled after a strict filtering and qualifying process. Among 33 prognostic microRNAs identified for esophageal cancer, miR-21 and miR-375 appeared more frequently. The median study size was 70.5 patients (29-249 patients) and the median HR was 3.305 (IQR = 1.615-7.31). For the studies evaluating miR-21's association with overall survival (OS), the pooled HR suggested that high level of miR-21 has a negative impact on OS (HR = 1.52[1.17-1.98], P = 0.001). As for miR-375, the pooled HR for OS (high/low) was 0.53 (95% CI: 0.39-0.73, P < 0.001), indicated that low level of miR-375 has a negative impact on OS. These results indicated that microRNAs show promising associations with prognosis in esophageal cancer. Up-regulation of miR-21 and down-regulation of miR-375 can predict unfavourable prognosis in esophageal cancer.