Snapshot A 59-year-old woman with recently diagnosed metastatic estrogen-receptor (ER) positive and human epidermal growth factor 2 (HER2) negative breast cancer presents for follow-up care. She is hormone therapy naive and has non-visceral involvement of the cancer. She is started on letrozole. Introduction Mechanism of action inhibits peripheral conversion of androgens to estrogens via aromatase inhibition Clinical use estrogen-receptor positive breast cancer first-line treatment in postmenopausal women to prevent recurrence Toxicity menopausal symptoms fatigue Medications letrozole anastrozole exemestane