ERBB4 and breast cancer: Although there were only 2 studies providing evaluable HRs for OS, the pooled HR implied that patients with Luminal breast cancer would benefit from high expression of HER4 with no significant heterogeneity detected (HR = 0.71, CI: 0.52–0.95, P = 0.020, fixed effects; P = 0.243, I2 = 26.7%; Figure 3B).