SIX6 and breast cancer: SIX6 was also found to be linked to poor OS of patients with luminal breast cancer (HR: 1.54, 95% CI: 1.06–2.25; P = 0.456 and I2 = 0.0%; Fig. 7C), but not associated with RFS (HR: 1.26, 95% CI: 0.96–1.64; P = 0.207 and I2 = 26.7%; Fig. 7D) of this subgroup.