Trastuzumab/Pertuzumab With Fulvestrant and Culmerciclib in HR+/HER2+ Early Breast Cancer

This phase II single-arm study is designed to evaluate the neoadjuvant efficacy of a chemotherapy-free regimen consisting of trastuzumab, pertuzumab, Culmerciclib, and fulvestrant in patients with treatment-naïve stage II-III hormone receptor-positive, HER2-positive breast cancer. The pathological complete response (pCR) rate serves as the primary endpoint. The study aims to assess whether the pCR rate meets or exceeds that achieved with standard chemotherapy plus dual HER2-targeted therapy, and to generate preliminary evidence to support the design of a future phase III randomized controlled trial.