ctDNA-Guided De-Escalation of Adjuvant Chemotherapy With Dalpiciclib in HR-Positive/HER2-Negative Breast Cancer

* This is a Phase II, multicenter, randomized clinical trial evaluating a ctDNA-guided approach to de-escalate adjuvant chemotherapy in patients with hormone receptor (HR)-positive, HER2-negative early-stage breast cancer. The study aims to determine if combining the CDK4/6 inhibitor Dalpiciclib with endocrine therapy can reduce the need for chemotherapy while maintaining clinical benefits. * Key Details ： 1. Participants: 393 women (aged 18-75) with early-stage HR+/HER2- breast cancer at high risk of recurrence (e.g., tumor size ≥2 cm, lymph node involvement, or high-grade tumors). 2. Design: Patients are randomized 1:4 to two groups: Group A (Chemotherapy) : Receives 4 cycles of taxane-based chemotherapy before surgery. Group B (Experimental) : Receives Dalpiciclib + aromatase inhibitor (AI) for 4 cycles pre-surgery. Post-surgery, treatment is adjusted based on ctDNA results. 3. Primary Goals ： Assess ctDNA clearance rate (conversion from detectable to undetectable ctDNA) after neoadjuvant therapy in Group B. Evaluate 3-year event-free survival (EFS) in Group B (e.g., freedom from cancer recurrence, progression, or death). Secondary Goals ： Safety of Dalpiciclib + endocrine therapy. Tumor response rates (e.g., complete cell cycle arrest, pathological remission). Correlation between ctDNA clearance and long-term outcomes. * Why This Matters ： Current guidelines recommend chemotherapy for high-risk HR+ breast cancer, but it often causes significant side effects. This study explores a personalized approach using ctDNA-a blood-based biomarker-to identify patients who may safely avoid chemotherapy without compromising survival. If successful, it could shift clinical practice toward less toxic, targeted therapies for eligible patients.