HR+/ HER2- Advanced/ Metastatic Breast Cancer Real World Treatment Patterns and Outcomes

Patient Characteristics, Treatment Patterns, and Clinical Outcomes in Patients Diagnosed With HR+/HER2- Advanced/Metastatic Breast Cancer Receiving CDK4/6i + Aromatase Inhibitor (AI) Combination Therapy as Initial Endocrine-based Treatment

This is a retrospective, observational study that will document the treatment patterns and clinical outcomes of patients diagnosed with HR+/HER2- A/MBC who received CDK4/6i combination therapy with aromatase inhibitors (AI) as the initial endocrine-based therapy in the A/MBC setting.

Inclusion Criteria:

1. Female or male sex.

2. Diagnosis (confirmed by clinical review) of A/MBC, defined as breast cancer at stage IIIB, stage IIIC, stage IV or identified as having distant metastasis.

3. Age ≥18 years at A/MBC diagnosis.

4. Initiated a CDK4/6i in combination with an AI as initial endocrine-based therapy after A/MBC diagnosis on or after 2/3/2015 and before 4/1/2019.

   •Note that the date of the start of the inclusion period reflects the month that the first CDK4/6i (ie, Palbociclib) received U.S. FDA approval.

5. Evidence of ER or PR positive disease, or absence of any indication of ER and PR negative disease closest to A/MBC diagnosis (ie, patients are eligible without affirmative indication of ER/PR+ status as long as ER/PR- indication is not present).

6. Evidence of HER2 negative disease, or absence of any indication of HER2 positive disease closest to A/MBC diagnosis (ie, patients are eligible without affirmative indication of HER2- status as long as HER2+ indication is not present).

Exclusion Criteria:

1. Enrollment in an interventional clinical trial for A/MBC during the study observation period.