CDK4 and breast cancer: Recent clinical trials—PALOMA-3, MONALEESA-3, and MONARCH-2 (fulvestrant combined with palbociclib, ribociclib, or abemaciclib) (35–38), as well as PALOMA-2, MONALEESA-2, and MONARCH-3 (AIs combined with the same CDK4/6 inhibitors)—have demonstrated significantly improved progression-free survival (PFS) and overall survival (OS) compared to fulvestrant or AI monotherapy (39–41) Additionally, targeting the PI3K/AKT/mTOR signaling cascade with mTOR inhibitors, such as everolimus, represents a significant advancement in BC therapy (42, 43).