Treatment Challenges for ESR1-Mutant Breast Cancer
December 9, 2025 • ESR1 Mutated ER HER2 Advanced Breast Cancer Content Hub
Matthew P. Goetz, MD, Mayo Clinic, Rochester, Minnesota, describes how resistance to endocrine therapy often develops in ER-positive breast cancer through emergence of ESR1 mutations, which occur in roughly 30% to 40% of patients previously treated with hormonal therapies. He notes that while newer agents, such as CDK4/6 inhibitors, have improved outcomes, the best strategy after progression, particularly which hormonal drug to use in combination therapy for ESR1-mutant disease, remains uncertain.
