High mRNA level of SIX1 was statistically associated with a poor OS (HR: 1.28, 95% CI: 1.03–1.58; P = 0.963 and I2 = 0.0%; Fig. 6A) and RFS (HR: 1.28, 95% CI: 1.05–1.56; P = 0.206 and I2 = 26.8%; Fig. 6B) of whole population of breast cancer. Here, SIX1 is linked to breast cancer.