<i>ESR1</i> Mutation in Endocrine Treatment-Naïve Endometrial Cancer: Prevalence, Characteristics, and Prognostic Implications, Results from the UTOLA Phase II GINECO Trial

ESR1 mutations, while rare overall in treatment-naïve endometrial cancer, are more prevalent in patients with NSMP low-grade endometrioid endometrial cancer, potentially affecting AI efficacy. ESR1 status should be considered in selecting hormonotherapy and as a stratification factor in AI trials.