Clinical Research Directory

Inclusion criteria: * Diagnosed with HR+/HER2- breast cancer. * No evidence of distant metastatic spread. * Underwent primary breast cancer surgery (mastectomy/lumpectomy) during the study period. * Initiated adjuvant ET within 12 months of surgery date and after September 17, 2024, to the period up to 3 months prior to the data cutoff date. * Had at least one visit during the baseline period and at least one visit one day after the index date. * Patients included must have met one of the following conditions at the time of diagnosis or surgery: 1. Nodal stage (N) N2 or N3 disease. 2. N1 any anatomic tumor size (T), including micrometastatic patients except T0 N1mi and T1 N1mi; For T0 N1mi and T1 N1mi patients with Grade 3 disease alone will be selected. 3. Node-negative with the following high-risk criteria: 1. Tumor size is T3, T4 2. Tumor size is T2 and Grade 3 3. Tumor size is T2 with Grade 2 and either Ki-67 score ≥ 20% or genomic high risk based on Oncotype Dx/Mammaprint/Endopredict/Prosigna Exclusion criteria: * Use of any prior CDK4/6i before the index date. * Missing T or N values for both clinical and surgical stage. * Diagnosis of cancer other than breast cancer. * Evidence of participation in a clinical trial at any time during the study observation period.