Beyond Breast Cancer: ESR1 Mutations Identified as Prevalent Primary Drivers in NSMP Low-Grade Endometrial Cancer

Introduction: The Shifting Landscape of Endometrial Cancer Management

In the evolving field of gynecologic oncology, the management of estrogen receptor (ER)-positive endometrial cancer (EC) has increasingly leaned toward targeted endocrine interventions. Aromatase inhibitors (AIs) have become a staple for treating low-grade endometrioid endometrial cancer (LGEC), particularly in advanced or recurrent settings. However, clinical experience often reveals a heterogeneous response to these therapies. In breast cancer research, mutations in the ESR1 gene, which encodes the estrogen receptor alpha, are well-established as a major mechanism of acquired resistance to AIs. These mutations typically emerge under the selective pressure of treatment and are rarely found in treatment-naive patients. The UTOLA phase II GINECO trial has recently provided groundbreaking data suggesting that the landscape of ESR1 mutations in endometrial cancer may differ significantly from that of breast cancer, with profound implications for primary treatment selection.

Study Highlights