Based on clinical trial evidence of improvements in progression-free survival (PFS) without a significant decline in health-related quality of life (QoL), cyclin-dependent kinase 4/6 (CDK4/6) inhibitors in combination with endocrine therapy (ET) are considered the standard of care in patients with hormone receptor–positive/human epidermal growth factor receptor 2–negative (HR+/HER2−) advanced or metastatic breast cancer (ABC) [1–6]. This evidence concerns the gene CDK4 and aneurysmal bone cyst.