Interleukin-6 as a prognostic marker for breast cancer: a meta-analysis

Aims and background: Interleukin-6 (IL-6) has been shown to promote tumor survival, metastasis, and angiogenesis, in addition to possessing antitumor activities. In light of the conflicting data, we sought to determine whether IL-6 could be used as a prognostic factor for patients with breast cancer. Methods: Eligible studies describing the use of IL-6 as a prognostic factor for breast cancer were identified. Data describing overall survival (OS), disease-free survival (DFS), and clinicopathologic features were collected and analyzed. Results: Thirteen articles containing 3,224 breast cancer patients were identified. The results showed that IL-6 expression was not associated with lymph node metastasis, tumor size, or histologic grade. Moreover, there was no correlation between IL-6 expression and DFS. However, the combined hazard ratio (95% confidence interval) for OS was 2.15 (1.46, 3.17). Sensitivity analysis further demonstrated that, for OS, the results of this meta-analysis were stable. A subgroup analysis showed that the source used to detect IL-6 levels may have altered the pooled results for OS. Conclusions: Taken together, these results indicate that IL-6 expression is associated with poor prognosis for breast cancer and the prognostic role is affected by the source used to detect IL-6 levels.