For example, a recent multicenter real-world study comparing first-line chemotherapy with CDK4/6 inhibitors in HR-positive, HER2-negative breast cancer with liver metastases demonstrated that, although progression-free survival favored CDK4/6 inhibitor therapy (10.9 vs. 4.8 months), overall survival was significantly longer with chemotherapy (42.2 vs. 25.9 months) (25). Here, CDK4 is linked to breast cancer.