RAD21 and cancer: Across all cancer-related genes that were assessed, only RAD21 mutations (currently not considered actionable/targetable with approved drugs) had significantly higher prevalence in stage IV HR+/HER2− tumors compared to stage I-III disease (18.4% vs 9.7%; FDR = 0.04; OR 2.1, 95% CI: 1.4-3.2; Supplementary Figure 1).