A Real-World Study of Early Breast Cancer Patients Eligible for Treatment With CDK4/6 Inhibitors

The aim of this study was to describe treatment patterns, patient characteristics and clinical outcomes among hormone receptor positive/human epidermal growth factor receptor 2 negative (HR+/HER2-) early breast cancer (eBC) patients who became eligible for treatment with cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) in the real-world setting after the FDA approval of ribociclib treatment for eBC. The study used data abstracted from structured and unstructured patient electronic health records from sites available in the Integra Connect PrecisionQ database (secondary data use).

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.