ESR1 and breast cancer: Similarly to the findings for BAL1, high levels of BAL2 were significantly associated with extended RFS across all BC patients (HR = 0.68, p = 4.7 × 10−7), as well as within ER-positive (HR = 0.79, p = 0.016), ER negative (HR = 0.48, p = 2.1 × 10−8), Basal(HR = 0.46, p = 7.3 × 10−7), luminal B (HR = 0.7, p = 0.0079), HER2- (HR = 0.72, p = 0.00018), HER2+ (HR = 0.57, p = 0.00029) subtypes, but not within luminal A subtype (HR = 0.81, p = 0.25) (Fig. 6A-H).