Inclusion Criteria:  Patients must meet all of the following inclusion criteria to be eligible for inclusion in the study:  Diagnosed with breast cancer (ICD-9 174.x or 175.x or ICD-10 C50x) At least two visits in the Flatiron database on or after January 1, 2011 Pathology consistent with breast cancer Has evidence of stage IV or recurrent metastatic breast cancer with a metastatic diagnosis date on or after January 1, 2011. This includes patients who were diagnosed with stage IV at diagnosis or were diagnosed with earlier stage disease, then developed a distant metastasis later on, or had recurrence of the disease via a distant metastasis Confirmed receipt of talazoparib as treatment for mBC via abstraction initiated between January 1, 2018 and September 30, 2020 HER2 negative test result on or before the start of patient's first talazoparib-containing line of therapy, as defined by Flatiron's line of therapy rules BRCA1, BRCA2, BRCA1 and BRCA2 germline mutation, or BRCA germline mutation not otherwise specified, identified on or before the start date of patient's first talazoparib-containing line of therapy, as defined by Flatiron's line of therapy business rules Age 18 years or older at the time of first talazoparib-containing line of therapy  Exclusion Criteria:  Lacking relevant unstructured documents in the Flatiron database for review by the abstraction team Receipt of drug as part of a clinical trial (captured in the database as "clinical study drug" without additional information about active ingredient or whether the patient received placebo), defined as any non-cancelled order, administration, or oral episode for a drug used in a clinical trial, on or prior to start of first talazoparib line of therapy, as defined by Flatiron's line of therapy business rules