Data from Clinical and Genomic Factors Associated with Elacestrant Outcomes in ESR1-Mutant Metastatic Breast Cancer

AbstractPurpose: ESR1 mutations mediate resistance to antiestrogen therapy in hormone receptor–positive metastatic breast cancer (MBC). Elacestrant, an oral selective estrogen receptor degrader, improves progression-free survival over standard endocrine therapy in ESR1-mutant MBC. We assessed real-world elacestrant use and clinical–genomic factors associated with outcomes. Experimental Design: This study used the GuardantINFORM database, linking >42,000 real-world breast cancer cases with sequencing and claims data. We included patients with activating ESR1 mutations detected