ERBB2 and breast cancer: Of note, in these exploratory subgroup analyses no PFS benefit with the addition of abemaciclib was found in patients with TFI ≥ 36 months (HR = 0.833; 95% CI 0.457–1.517); in comparison, patients with a TFI > 36 months in MONALEESA-2 did have a PFS benefit with ribociclib + letrozole (Blackwell KL et al. Subsequent treatment for postmenopausal women with hormone receptor-positive, HER2-negative advanced breast cancer who received ribociclib + letrozole vs placebo + letrozole in the Phase III MONALEESA-2 study.