Background: BRCA1/2 mutations account for 5-10% of breast cancer (BC) patients. BRCA1 mutations are associated with aggressive tumors, often triple negative (TNBC) (HER2, estrogen-receptor [ER], progesterone-receptor [PR] negative) and are mainly treated with combination chemotherapy or platinum agents. This study aimed to compare real world treatment patterns in breast cancer patients who were BRCA-mutation positive (BRCA+) and those who were BRCA-mutation negative (BRCA-), focusing on hormone-receptor positive (HR+) and TNBC subgroups. Methods: Optum’s Humedica electronic health records (EHR) database was used to identify a cohort of women with 1) confirmed BC ICD-9/ICD-10 diagnosis between 2008 and 2018, 2) at least 12 months of history in EHR, 3) at least one distant metastasis diagnosis (per ICD-9/ICD-10 or physician notes), and 4) no previous diagnosis of other primary cancers in previous 12 months. HR and HER2 test results were used to create relevant subgroups. Distinct lines of therapy (LOT) in the post-metastatic period were established using business rules. Treatment patterns and duration of treatment were analyzed. Results: Among 65,934 metastatic BC patients identified, 7941 were BRCA+, of whom 5366 (68%) were HR+ and 1323 (17%) had TNBC phenotype, while 4027 were BRCA-, of whom 2859 (71%) were HR+ and 561 (14%) had TNBC phenotype. Seventy-one percent of BRCA+ women underwent drug treatment, compared to 65% of BRCA- women. Drug treatments included hormonal treatment (+/-other agents), targeted therapy, and chemotherapy only, and varied across the different cohorts (Table). Mean (median) duration of treatment in LOT1 in the BRCA+ and BRCA- cohorts was 117 (73) and 117 (72) days, respectively. Conclusions: Real-world evidence on treatment patterns in BC patients revealed substantial differences across important biomarker and hormonal status BC phenotypes. As a preponderance of women with TNBC are still being treated exclusively with chemotherapy, these data highlight how the need for development of effective treatment options for TNBC remains high.