Meta-analysis of STAT3 and phospho-STAT3 expression and survival of patients with breast cancer

The prognostic value of signal transducer and activator of transcription 3 (STAT3) and phospho-STAT3 in breast cancer remains controversial in heterogeneous. The objective of this meta-analysis was to evaluate STAT3 and phospho-STAT3 expression on the prognosis of breast cancer patients.

PubMed, Cochrane Central Register of Controlled Trials, Embase, Web of Science, Chinese CNKI, and Wan Fang were searched up to 19th June 2017. Studies which investigated the STAT3 or phospho-STAT3 expression of patients with breast cancer on the basis of patient survival data or survival curve were eligible.

This meta-analysis involves 12 studies and 4513 female patients with breast cancer. No clear relationship exists between overall survival (OS) and high expression of STAT3 and p-STAT3 (hazard ratio [HR] = 0.95, 95% confidence interval [CI]: 0.62-1.46, p > 0.05). p-STAT3 expression is unrelated to disease-free survival (HR = 0.69, 95% CI: 0.18-2.55, p = 0.573). Notably, the pooled effect predicts better breast cancer-specific survival with p-STAT3 overexpression (HR = 0.68, 95% CI: 0.59-0.78, I² = 30.9%, p < 0.001). Results of subgroup analyses show that STAT3 overexpression indicates shorter OS (HR = 1.87, 95% CI: 1.42-2.45, p < 0.001) when excluding the heterogeneity test. Meanwhile, p-STAT3-positive patients have a significantly higher OS than their counterparts (HR = 0.72, 95% CI: 0.57-0.91, p < 0.01).

Positive STAT3 expression may indicate poor OS. However, p-STAT3, as a potential molecular biomarker for predicting chemotherapeutic effect, appears to have better prognostic value than STAT3.