On subgroup analysis classified in cancer type, high SIX1 expression was associated with poor overall survival in patients with hepatocellular carcinoma (HR 1.50; 95% CI: 1.17-1.93, <i>P</i> =0.001), breast cancer (HR 1.31; 95% CI: 1.10-1.55, <i>P</i> =0.002) and esophageal squamous cell carcinoma (HR 1.89; 95% CI: 1.42-2.52, <i>P</i><0.0001). This evidence concerns the gene SIX1 and breast cancer.