Guideline Summary Use of Biomarkers to Guide Decisions on Systemic Therapy for Women With Metastatic Breast Cancer: American Society of Clinical Oncology Clinical Practice Guideline

ASCO has published evidence-based recommendations for practicing oncologists and other stakeholders on the appropri-ate use of results from assays of breast tumor biomarkers to guide or influence decisions on systemic therapy in womenwith metastatic breast cancer.1 The guideline addressed four overarching clinical questions: (1) Under what circumstances (ie, for which patients) should metastases be biopsied or otherwise sampled to test for changes from the primary tumor with respect to endo-crine receptor or human epidermal growth factor receptor 2 (HER2) status? (2) For women withmetastatic breast cancer and with known endocrine receptor and HER2 status, which additional tumor markers have demonstrated clinical utility to guide initiation of systemic therapy or direct selection of a ne