The pooled OR of 7 studies with substantial heterogeneity (I2 = 70.5%) indicated that CXCR4 expression was increased in lung cancer with distant metastasis compared to lung cancer without distant metastasis (OR 3.65, 95% CI 1.53–8.68, P = 0.003) (Fig. 3d). Here, CXCR4 is linked to lung cancer.