This American Society of Clinical Oncology (ASCO) clinical practice guideline provides treatment recommendations for women with hormone receptor (HR)-positive metastatic breast cancer (MBC) who are being considered for endocrine therapy. These guidelines were developed for implementation across health settings and include the following ASCO recommendations:

• Except in cases of immediate life-threatening disease, hormone therapy, alone or in combination, should be used as initial treatment.

• Patients whose tumors express any level of hormone receptors should be offered hormone therapy.

• Treatment recommendations should be based on type of adjuvant treatment, disease-free interval, and organ function.

• Tumor markers should not be the sole criteria for determining tumor progression; use of additional biomarkers remains experimental.

• Assessment of menopausal status is critical; ovarian suppression or ablation should be included in premenopausal women.

• For postmenopausal women, aromatase inhibitors (AIs) are the preferred first-line endocrine therapy, with or without the cyclin-dependent kinase inhibitor palbociclib.

• As second-line therapy, fulvestrant should be administered at 500 mg with a loading schedule and many be administered with palbociclib.

• The mammalian target of rapamycin inhibitor everolimus may be administered with exemestane to postmenopausal women with MBC whose disease progresses while receiving nonsteroidal AIs.

• Among patients with HR-positive, human epidermal growth factor receptor 2–positive MBC, human epidermal growth factor receptor 2–targeted therapy plus an AI can be effective for those who are not chemotherapy candidates.

Citation: Rugo HS, Rumble B, Macrae E, et al. Endocrine therapy for hormone receptor-positive metastatic breast cancer: American Society of Clinical Oncology guideline. [Published online ahead of print May 23, 2016]. J Clin Oncol. doi:10.1200/JCO.2016.67.1487.