Considering the subgroup analyses of IL‐6, heterogeneity was reduced in European studies (I2 = 0.0%, Ph = 0.679), studies that examined patients aged ≥ 60 years (I2 = 0.0%, Ph = 0.679), and GBM studies (I2 = 0.0%, Ph = 0.397). This evidence concerns the gene IL6 and glioblastoma.