Description of Treatment Patterns and Description and Comparison of Healthcare Resource Utilization and Costs of Women With Metastatic HR+/HER2- Breast Cancer Treated With CDK4/6 Inhibitors

The study was an observational, retrospective cohort design, using US administrative insurance claims data, to better understand Healthcare resource utilization (HRU) and healthcare costs among women with mBC initiated on a CDK4/6 inhibitor.

This study used an observational, retrospective cohort design, using US administrative insurance claims data, previously employed in an existing project, to better understand HRU and healthcare costs among women with mBC initiated on a CDK4/6 inhibitor.

Adult women with HR+/HER2- mBC initiated on a CDK4/6 inhibitor were included in the study and were stratified into cohorts based on the first CDK4/6 inhibitor they received (i.e., abemaciclib, palbociclib, or ribociclib), regardless of the line of therapy and menopausal status.

The initiation of the first CDK4/6 inhibitor was defined as the index date. The index treatment was defined as the CDK4/6 inhibitor initiated on the index date (i.e., abemaciclib, palbociclib, or ribociclib).

The 6-month period preceding the index date was considered as the baseline period, and was used to measure patient characteristics.

Outcomes were measured between the index date and 1) the end of the study period (persistence, switch, HRU, costs) OR 2) the end of the index treatment (adherence, dose modification, frequency of monitoring), as relevant. The end of the study period was defined as the earliest occurrence between the end of continuous enrollment and the end of data availability.

Eligibility Criteria:
Inclusion Criteria:

- Evidence of treatment with a CDK4/6 inhibitor regardless of the line of therapy.

The initiation of the first CDK4/6 inhibitor was defined as the index date, and the first CDK4/6 inhibitor initiated was defined as the index treatment

* BC diagnosis: Two diagnosis codes of BC (International Classification of Diseases, 9th Revision, Clinical Modification \[ICD-9-CM\]: 174.xx and International Classification of Diseases, 10th Revision, Clinical Modification \[ICD-10-CM\]: C50.xx \[excluding C50.x2 - male BC\]) on two medical service claims separated by at least 30 days
* Metastatic disease diagnosis: At least two medical claims for a secondary neoplasm (ICD-9-CM codes: 196.xx-197.xx, 198.xx, ICD-10-CM codes: C77.xx, C78.xx, C79.xx) on separate dates, with the first one occurring no more than 30 days before the first diagnosis for BC
* HR+/HER2-: At least one prescription fill or administration of an ET (anastrazole, exemestane, ethinyl estradiol, fulvestrant, fluoxymesterone, letrozole, megestrol acetate, tamoxifen, or toremifene), HR+/HER2- therapy (everolimus), or CDK4/6 inhibitor (i.e., abemaciclib, palbociclib, or ribociclib) at any time following the diagnosis of BC, and no claims for treatments indicated for HER2+ BC, including trastuzumab, lapatinib, afatinib, pertuzumab, or ado-trastuzumab, at any time in the data period
* Women of at least 18 years of age as of the index date
* At least 6 months of continuous health plan coverage prior to and at least 1 month of continuous health plan coverage after the index date

Exclusion Criteria:

* None