Observational Retrospective Study to Assess the Use of Ribociclib in Patients With HR+, HER2- Metastatic Breast Cancer Treated With Chemotherapy

Inclusion Criteria:

Group I: Postmenopausal female patients who had histologically or cytologically confirmed HR-positive (10% or more ER+), HER2-negative, metastatic breast cancer and initiated ribociclib combinations per local label.

* Treated with ribociclib plus letrozole relapsed after 12 months completing adjuvant treatment or without any prior endocrine treatment for metastatic disease, 1 line or less chemotherapy was allowed.
* Treated with ribociclib plus fulvestrant, clinical and/or radiological disease progression after at least 6 months and at least 1 aromatase inhibitor treatment for metastatic disease or relapsed after 12 months adjuvant aromatase inhibitor treatment and/or relapsed within 12 months completing adjuvant aromatase inhibitor, 2 lines or less prior treatments and 1 line or less prior chemotherapy at metastatic setting were allowed.
* Had first treatment response rate assessment within 6 months after ribociclib initiation.
* Initiated ribociclib in combination with letrozole/fulvestrant after MBC diagnosis after local approval of ribociclib in June 2020.

Group II: Postmenopausal female patients who had histologically or cytologically confirmed HR-positive (10% or more ER+), HER2-negative, metastatic breast cancer eligible for cyclin-dependent kinase (CDK) inhibitors according to local label but started chemotherapy.

Exclusion Criteria:

* Pre- or perimenopausal women.
* Enrollment in an interventional clinical trial for MBC during the study observation period.
* Evidence of prior treatment with any CDK4/6 inhibitor in the adjuvant setting.
* Evidence of another primary cancer within 3 years prior to the initial line containing ribociclib.