Table 1.

Population, intervention, comparison, outcomes and study design (PICOS) criteria

Criteria	Inclusion criteria	Exclusion criteria
Population	Adult patients aged ≥ 18 years diagnosed with breast cancer within and across disease stages (early and metastatic) and by molecular subtypesa	Only patients aged < 18 years All other diseases
Intervention/comparators	Various treatment patterns/strategies of CDK4/6i Use as first-line vs second-line or later Subsequent therapy following CDK4/6i use in metastatic breast cancer	Studies that do not discuss treatment patterns/strategies of CDK4/6ib
Outcomes	Characteristics of patients who received CDK4/6i for metastatic breast cancer across all potential treatment patterns Clinical outcomes of patients who received various CDK4/6i treatment strategies for metastatic breast cancer	Studies that do not report any relevant outcomesb
Study design	Peer-reviewed publications, including: Narrative and systematic literature reviews (initial search conducted for reviews since 1 January, 2018; then further limited to since 1 January, 2021 because of a large number of reviews identified after 2018) Clinical studies (e.g., RWE studies, clinical trials) (since 1 January, 2015) Gray literature Conference abstracts (since 1 January, 2018) Clinical trial registry records (since 1 January, 2015)	Narrative and systematic literature reviews published prior to 2018 Conference abstracts published prior to 2018 Clinical studies and clinical trial registry records published prior to 2015
Language	English	Non-English

CDK4/6i cyclin-dependent kinase 4/6 inhibitor, ER estrogen receptor, HER2 human epidermal growth factor receptor 2, RWE real-world evidence, TNBC triple-negative breast cancer

^aIncludes all molecular subtypes of breast cancer (e.g., ER+/−, HER2+/−, TNBC; i.e., luminal A/B, HER2 enriched, basal breast cancer)

^bExcludes clinical trials that evaluate the efficacy and safety of CDK4/6i but do not report treatment patterns or place in therapy of CDK4/6i across multiple lines of therapy