ASCO	American Society of Clinical Oncology
CCI	Charlson Comorbidity Index
CDK4/6	Cyclin-dependent kinase 4 and 6
CDK4/6i	Cyclin-dependent kinase 4/6 inhibitor
CDK4/6i-PFS	Progression-free survival from CDK4/6 inhibitor initiation
CI	Confidence interval
ECOG	Eastern Cooperative Oncology Group
ESMO	European Society for Medical Oncology
ESS	Effective sample size
HER2	Human epidermal growth factor receptor 2
HR	Hazard ratio
HR-positive	Hormone receptor-positive
IPTW	Inverse probability of treatment weighting
IQR	Interquartile range
OS	Overall survival
PFS	Progression-free survival
PFS2	Progression-free survival after two lines of therapy
PS	Propensity score