CXCL12 and breast cancer: Based on unadjusted univariate and adjusted multivariate regression models and single-biomarker ROC and Kaplan–Meier survival curves, we found that apart from low SDF-1α (<42 pg/dL) levels, a low number of circulating EPCs (<9.68 cells/μL) may also serve as a single biomarker for shorter DFS in breast cancer patients.