The value of CD9 as a prognostic predictor for various human malignant neoplasms: a meta-analysis

Background: Recent studies indicate that the correlation in the expression level of CD9 and the prognosis differs from tumor types. This meta-analysis was performed to illustrate the predictive value of CD9. Methods This analysis included 13 studies involving a total of 1231 patients. We used PubMed, Cochrane Library, Web of Science and Embase for comprehensive literature search and manual search for related bibliography. To probe into the relationships between CD9 expression and patient prognosis, pooled hazard ratios (HRs) with 95% confidence intervals (CIs) were used to describe patient survival and disease recurrence. Results This meta-analysis contained 13 eligible studies. High expression of CD9 indicate worse overall survival (OS) (the polled HR = 1.14, 95%CI: 0.66–1.99), although the result was not statistically significant (P = 0.638).Moreover high expression of CD9 could not result in the worse disease-free survival (DFS) / recurrence-free survival (RFS) of the tumor patients (the pooled HR = 0.67, 95% CI: 0.24–1.87; P = 0.445). Conclusions The expression of CD9 could not be used to regard as an independent prognostic predictor.