Precision Treatment of HR+ HER2- Advanced Breast Cancer Based on SNF Molecular Subtyping

This is a randomized, controlled, open-label, phase II study to explore the efficacy and safety of a three-drug combination of Everolimus or Fluzoparib plus Fulvestrant and Abemaciclib compared to a two-drug combination of Fulvestrant plus Abemaciclib in patients with HR+ HER2-advanced breast cancer of SNF1/SNF3 subtype who have progressed after CDK 4/6 inhibitor treatment. The study consists of Safety Lead-in phase, which aims to explore the safety and preliminary efficacy of the three-drug combination, and phase II, which aims to explore the efficacy of the three-drug combination.