SIX1 and breast cancer: High SIX1 contributed to poor OS (HR: 1.64, 95% CI: 1.13–2.39; P = 0.705 and I2 = 0.0%; Fig. 7A) and RFS (HR: 1.43, 95% CI: 1.06–1.93; P = 0.112 and I2 = 38.4%; Fig. 7B) of luminal breast cancer patients.