Background/Rationale: Within the setting of metastatic human epidermal growth factor receptor 2 negative (HER2-ve) breast cancer limited epidemiological data exist on the prevalence of pathogenic mutations of breast cancer susceptibility gene (BRCA) and other homologous recombination repair (HRR) genes. There are also limited data on the treatments and clinical outcomes of patients with such germline and somatic genetic profiles, particularly within this setting. This epidemiologic study will estimate the prevalence of germline breast susceptibility gene (gBRCA) mutations among metastatic HER2-ve patients who have commenced 1st line systemic cytotoxic chemotherapy and, at that time, are considered to have exhausted hormone therapy options (if hormone receptor positive \[HR+ve\]), per investigator's opinion. Among those patients with a gBRCA gene mutation, treatment patterns and clinical outcomes will be described. This study may also explore the prevalence of somatic BRCA (sBRCA) mutations and other HRR gene mutations among metastatic HER2-ve patients who have commenced 1st line systemic cytotoxic chemotherapy. The treatment patterns and clinical outcomes may be described among those patients with a sBRCA gene mutation and those with other HRR gene mutations.
