Long-term Clinical Benefit of Sacituzumab Govitecan in Metastatic HR+/HER2- Breast Cancer Despite Discordant Radiologic Progression over a 24-year course: A Case Report

Introduction

Hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER 2–) breast cancer (BC) accounts for ∼70% of cases. First-line endocrine therapy plus cyclin-dependent kinase 4/6 (CDK4/6) inhibitor is standard, yet many patients eventually develop endocrine resistance, limiting long-term benefit. Antibody-drug conjugates (ADC) offer a targeted approach for advanced disease. Sacituzumab govitecan (SG), a first-in-class Trop-2 ADC, is approved for metastatic HR+/HER2– BC and has shown improved clinical outcomes and quality of life (QoL) than standard chemotherapy in pretreated, endocrine-resistant patients. Case Presentation: We report a patient with metastatic HR+/HER2– BC and a 24-year treatment history who received SG as tenth-line therapy, after progression on multiple endocrine/radio/chemo/targeted regimens. Despite initial imaging indicating disease progression, continued SG treatment led to improved clinical symptoms, better QoL, and reduced lesion count, achieving 11 months of progression-free survival. After subsequent progression, the patient switched to trastuzumab deruxtecan (11th line); with no improvement after 1 cycle. The patient decided to discontinue treatment and ultimately succumbed due to disease progression.