HR Positive, HER2 Positive Breast Cancer

This is a single-arm, prospective, multicenter, phase II clinical study evaluating the efficacy and safety of a chemotherapy-free neoadjuvant regimen in patients with HR-positive/HER2-positive (HR+/HER2+) early or locally advanced breast cancer. Approximately 33 treatment-naive patients with stage II-III (AJCC 8th edition) HR+/HER2+ breast cancer will receive 5 cycles of neoadjuvant treatment with culmerciclib (a CDK4/6 inhibitor) plus letrozole, trastuzumab (TQB211) and pertuzumab (TQB2440), followed by definitive breast surgery. The primary endpoint is breast pathological complete response rate (bpCR, ypT0/is ypN0). Secondary endpoints include objective response rate (ORR), residual cancer burden (RCB), Ki67 change rate, patient-reported outcomes, and safety assessed per CTCAE v5.0.