The pooled results of two studies [13, 17] showed that a high tumor expression of CXCL12 was associated with poorer PFS in patients with GC (HR: 1.52, 95% CI 1.05–2.20, p = 0.03; Fig. 5) with no significant heterogeneity (p for Cochrane Q test = 0.76; I2 = 0%). Here, CXCL12 is linked to gastric cancer.