A Prospective, Multicenter, Randomized, Open-Label Phase II Study of ctDNA-Guided De-Escalation of Adjuvant Chemotherapy With Dalpiciclib in HR-Positive/HER2-Negative Breast Cancer
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.
• Female breast cancer patients aged ≥18 years and ≤75 years, either postmenopausal or premenopausal/perimenopausal;
• Pathologically confirmed hormone receptor-positive (HR+), HER2-negative invasive breast cancer:
‣ ER-positive and/or PR-positive defined as: ≥10% of tumor cells showing positive staining;
⁃ HER2-negative defined as: standard immunohistochemistry (IHC) result of 0/1+; or IHC 2+ with negative in situ hybridization (ISH) (confirmed by the central pathology laboratory);
• At least one evaluable lesion per RECIST 1.1, with clinical staging meeting:
‣ T1c-3N0M0 with high-risk factors (Grade 3, or Grade 2 with Ki67 ≥20%);
⁃ Any TN+M0;
• Eastern Cooperative Oncology Group (ECOG) performance status score of 0-1;
• Willing to participate in the study and voluntarily sign informed consent;
• Agree to undergo ctDNA testing during treatment;
• Adequate organ and bone marrow function defined as:
‣ Absolute neutrophil count (ANC) ≥1,500/mm³ (1.5 × 10⁹/L) (without granulocyte colony-stimulating factor \[G-CSF\] treatment within 14 days);
⁃ Platelet count (PLT) ≥100,000/mm³ (100 × 10⁹/L) (without corrective therapy within 7 days);
⁃ Hemoglobin (Hb) ≥9 g/dL (90 g/L) (without corrective therapy within 7 days);
⁃ Serum creatinine ≤1.5× upper limit of normal (ULN) or creatinine clearance ≥60 mL/min (without corrective therapy within 7 days);
⁃ Total bilirubin (TBIL) ≤1.5×ULN (without corrective therapy within 7 days);
⁃ Aspartate aminotransferase (AST/SGOT) and alanine aminotransferase (ALT/SGPT) ≤1.5×ULN (without corrective therapy within 7 days);
⁃ Cardiac function: left ventricular ejection fraction (LVEF) ≥55%; QTc interval corrected by Fridericia's formula (QTcF) \<470 msec on 12-lead ECG;
• Women of childbearing potential must have a negative serum pregnancy test within 7 days prior to randomization and agree to use non-hormonal contraception from informed consent signing until 2 months after the last treatment.