For patients with ER+/HER2- advanced breast cancer, current treatment guidelines recommend the use of endocrine therapy plus a CDK 4/6 inhibitor as a first-line treatment. And while the guidelines recommend sequential endocrine therapy for disease progressions, this progression can lead to ESR1 mutations and resistance to endocrine therapy. Could a novel oral selective estrogen receptor have more efficacy in preventing ESR1 mutations associated with endocrine resistance? That’s the exact question the EMERALD trial sought to answer, and what this study found in its subgroup analyses is the focus of this Audio Abstract.