A Real-World Study of Treatment Patterns, Tolerability and Effectiveness of CDK4/6 Inhibition in HR+, HER2-negative Metastatic Breast Cancer Patients

Inclusion criteria

• Included in Flatiron's mBC Enhanced Data Model (EDM):

• Had an International Classification of Diseases (ICD) diagnosis of breast cancer (ICD, 9th revision, clinical modification [ICD-9-CM] 174.x or 175.x or ICD, 10th revision, clinical modification [ICD-10-CM] C50x)
• At least two documented clinical visits, on different days, occurring on or after January 1, 2011
• Included in probabilistic sample of patients queued for review via abstraction
• Had pathology consistent with breast cancer
• Had evidence of stage IV or recurrent mBC with a metastatic diagnosis date on or after January 1, 2011, including patients diagnosed as stage IV at initial diagnosis, or diagnosed with earlier stage disease who then developed metastatic disease
• Initiated treatment with first-line (1L) ribociclib (in combination with endocrine therapy [ET]) in the metastatic setting on or after January 1, 2018, and at least 6 months prior to the study data cutoff date (October 31, 2024) to ensure adequate time to observe dose modifications and treatment discontinuations
• Had evidence of HR+/HER2- test result prior to or up to 30 days after initiation of 1L ribociclib
• Had 1L ribociclib on or before April 30, 2024, to allow for at least 6 months of potential follow-up time prior to the data cutoff date of October 31, 2024

Exclusion criteria

• Use of any CDK4/6 inhibitor therapy in combination with tamoxifen
• Use of any CDK4/6 inhibitor in the pre-metastatic setting