ERBB2 and breast carcinoma: The MONARCH-3 study revealed that in postmenopausal HR+/HER-2- advanced breast cancer patients who had not previously received systemic therapy, the median PFS of the abemaciclib group was significantly longer than that of the endocrine therapy group (28.2 months vs. 14.8 months), with ORRs of 49.7% and 37%, respectively (13).