CXCR4 and breast cancer: However, breast cancers with CXCR4 expression were associated with lymph node status (pooled RR =1.20, 95% CI: 1.01-1.43, P<0.001 and I2 = 80.9 random-effect) and distant metastasis (pooled RR =1.52, 95% CI: 1.17-1.98, P = 0.125 and I2 = 42.1 random-effect) (Figure 2b,c).