European Treatment Patterns and Outcomes Associated With First-Line CDK4/6 Inhibition and Hormonal Therapies

Inclusion Criteria: * Is male or female * Has histologically or cytologically confirmed breast cancer diagnosis (HR+/HER2- breast cancer) * Has received a diagnosis of locally advanced breast cancer not amenable to curative radiation or surgical cure or of metastatic breast cancer (i.e., advanced breast cancer \[ABC\]); diagnosis may be de novo (initial diagnosis at ABC stage) or recurrent from earlier-stage disease (initial diagnosis of earlier-stage disease with subsequent progression to advanced disease) * Has initiated a required first-line therapy of interest: Palbociclib plus AI as first-line therapy for ABC between September 1, 2016, and July 31, 2020, or AI monotherapy as first-line therapy for ABC between January 1, 2010,, and July 31, 2020 * Was aged 18 years or older at the time of diagnosis of ABC * Is living or deceased at the time of record abstraction * Has a complete medical record, covering treatment for ABC, including any transfer record from other facilities (if applicable) that is available to the abstractor for data abstraction Exclusion Criteria: * The patient's first treatment after ABC diagnosis was chemotherapy (including induction chemotherapy) * The patient has evidence of other active malignant neoplasms within 3 years (except nonmelanoma skin cancer or carcinoma in situ) prior to diagnosis of ABC; patients diagnosed with second primary cancer after ABC diagnosis will not be excluded * The patient has evidence of prior treatment with any CDK4/6 …