The main aim of this study was to describe the profile of hormone receptor positive/human epidermal growth factor receptor 2 negative (HR+/HER2-) metastatic breast cancer (mBC) patients who received first-line (1L) current treatment options with ribociclib in the United States (US) clinical practice.

This study used administrative claims data. De-identified patient-level data of adult patients with HR+/HER2- mBC who initiated 1L treatment with a cyclin dependant kinase 4/6 inhibitor (CDK4/6i) i.e., ribociclib from the Komodo Health Solutions Research Database (KRD; data from 1 January 2016 to 30 June 2023) was used. Data included medical and pharmacy claims for insured patients, which had already been collected (i.e., secondary use of data).

Inclusion criteria:

• Had 1 or more paid pharmacy claims for ribociclib with the first claim for the CDK4/6i observed between 26 February 2018 and 31 December 2022 (i.e., during the index period)

  • With the index CDK4/6i used in combination with an endocrine-based therapy, that is an aromatase inhibitor (i.e., letrozole, anastrozole, or exemestane), or fulvestrant, as 1L treatment for mBC
  • With the endocrine therapy (ET) initiated within 60 days of the first paid pharmacy claim of the index CDK4/6i; ET may have been initiated no earlier than 60 days prior to the index date (expected window for insurance approval of the CDK4/6i as 1L treatment for mBC in a real-world setting)

• Adult who was 18 years of age or older as of the index date

• Had 2 or more medical service claims with a code for breast cancer (BC) separated by 30 days or more, and 1 or more claims with a code for BC prior to the index date

• Had 2 or more medical service claims with a code for a secondary neoplasm separated by 30 days or more, with the first code for a secondary neoplasm occurring not earlier than 30 days from the first diagnosis for BC, and 1 or more claims with a code for a secondary neoplasm prior to the index date

• Had continuous health plan enrollment for 12 months or more prior to and 1 month or more after the index date

Exclusion criteria:

• Patients who did not meet the inclusion criteria
• Had a diagnosis for other primary cancers (other than BC) before the first diagnosis for secondary neoplasm
• Had prior treatments for BC (i.e., chemotherapy, targeted therapy, ET [except ≤60 days prior to index date], or immunotherapy) during the 12-month washout period (relapsed/progressed ≤12 months prior to index date)
• Had prior surgical procedure for BC during the 12-month washout period (relapsed/progressed ≤12 months prior to index date)
• Had evidence of participation in a clinical trial prior to or at the index date (International Classification of Disease, 10th Edition, Clinical Modification [ICD-10-CM]: Z00.6)

This was a retrospective, non-interventional cohort study.