In ER-positive HER2-negative advanced BC, both ORR and mPFS significantly improved when used as first-line therapy in 493 postmenopausal women vs. placebo control (HR, 0.54; 95% CI, 0.41 to 0.72; p = 0.00002; MONARCH-3) [51]. This evidence concerns the gene ERBB2 and breast cancer.