Clinical Research Directory

Study Period: ENCORE database 1 (EDB1): Patient identification period: 01/01/2011-04/30/2024 with follow-up information through data cut-off date on 04/30/2024 ENCORE database 3 (EDB3): Follow-up information through June 2023 (there is no specific time period restrictions for patient eligibility) ENCORE database 4 (EDB4): Patient identification period: 10/01/2018-09/30/2023 with follow-up information through data cut-off date on 09/30/2023. Inclusion Criteria: * Age ≥18 years * Postmenopausal women with ER-positive, HER2-negative locally advanced or metastatic breast cancer who receive treatment without curative intent * The line of therapy for patients in EDB1 and EDB3 is implicitly advanced/metastatic because the line of therapy classification starts after their advanced/metastatic diagnosis in the respective database * In EDB4, patients must explicitly have any evidence of a metastasis prior initiating palbociclib plus letrozole or letrozole alone * Adenocarcinoma histology * No prior systemic treatment for advanced/metastatic disease * ECOG performance status of 0 or 1 Exclusion Criteria: * HER2+ * CNS metastases * Prior treatment with CDK4/6 inhibitor * Non-breast cancer malignancy other than basal/squamous cell skin cancer or carcinoma in situ of cervix * Systemic anticancer therapy other than palbocicilib or letrozole * Treatment with non-steroidal aromatase inhibitor (i.e.anastrozole, letrozole)