ESR1 Mutations and Overall Survival on Fulvestrant versus Exemestane in Advanced Hormone Receptor–Positive Breast Cancer: A Combined Analysis of the Phase III SoFEA and EFECT Trials

PURPOSE: circulating tumor DNA (ctDNA) analysis in the two phase III randomized trials of fulvestrant versus exemestane. EXPERIMENTAL DESIGN: mutation status on progression-free (PFS) and overall survival (OS) in a combined analysis of both studies. RESULTS: = 0.69). CONCLUSIONS: mutations in baseline ctDNA is associated with inferior PFS and OS in patients treated with exemestane versus fulvestrant.