CDK4 and breast cancer: Postoperatively, 75% received systemic treatment, varying by BC molecular subtype: cytotoxic chemotherapy (45%; e.g. alkylating agents, anthracyclines, taxanes, platinum-based antineoplastics, vinca alkaloids, nucleotide analogs, inhibitors of topoisomerase I/II), anti-HER2 therapy (36%), endocrine therapy (34%), CDK4/6, immune checkpoint (ICI) and PARP inhibitor therapy (each < 5%, Supplemental Table 1 and Fig. 1).