Long-Term Sacituzumab Govitecan Treatment in HR+/HER2- Advanced Breast Cancer: A Case Discussion

Introduction: Hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER 2–) breast cancer (BC) accounts for ~70% of BC cases. Guidelines recommend endocrine therapy with cyclin-dependent kinase 4/6 (CDK4/6) inhibitor as first-line treatment, but endocrine resistance significantly impacts patient outcomes. Antibody-drug conjugates (ADCs) represent a promising advancement in treating advanced disease by targeted delivery of cytotoxic agents. Sacituzumab govitecan (SG), a first-in-class ADC targeting Trop-2, is approved for patients with metastatic HR+/HER2–, showing improved clinical outcomes and quality of life (QoL) than standard chemotherapy in patients pretreated with systemic therapy, endocrine-resistant HR+/HER2– advanced BC. Case presentation: This case presents a 24-year treatment history of a patient with metastatic HR+/HER2– BC who received SG treatment as a tenth line of therapy, after progression on multiple lines of endocrine/radio/chemo/targeted therapies. Despite initial imaging indicating progressive disease (PD), continued SG treatment improved clinical symptoms, QoL, and reduced lesion count, achieving a progression-free survival of 11 months. After subsequent progression, the patient switched to trastuzumab deruxtecan (11 ^th line); with no improvement after 1 cycle. The patient decided to discontinue treatment and ultimately succumbed due to PD. Conclusion : SG demonstrated long-term clinical benefit in pretreated patients with metastatic HR+/HER2− BC. Clinical and biochemical improvements occurred within 2 cycles, while reduction of target lesions became apparent in subsequent cycles (likely influenced by tumor biology and prior treatments). In advanced, post-treatment stages of HR+ BC, with complex tumor biology and progression patterns, an individualized management combining diagnostic profiling, clinical monitoring, and comprehensive assessment of treatment effect is critical. Clinical trial number: Not applicable.