In addition, as shown in Fig. 2, high HIF-1α expression was strongly associated with MVD of bone tumor (SMD = 2.34, 95% CI 1.35–3.34, P <  0.001; random effects model: χ2 = 69.97, I2 = 91.4, P <  0.001). This evidence concerns the gene HIF1A and bone neoplasm.