Pyrotinib 320mg po qd d1-d21 q3w and Trastuzumab 600mg IH d1 q3w Combined with Dalpicicli 125mg po gd d1-d21 q4w

The DIAMOND study (DIAMOND-01) is a multicenter, randomized, open-label, non-inferiority Phase III clinical trial conducted by Fudan University Shanghai Cancer Center. The study aims to evaluate the efficacy and safety of an oral, "non-intravenous" regimen (pyrotinib + trastuzumab \[subcutaneous\] + dalpiciclib) compared to a standard intravenous chemotherapy-containing regimen (pyrotinib + trastuzumab \[subcutaneous\] + docetaxel) in patients with advanced HER2-positive breast cancer. Approximately 502 patients with histologically confirmed advanced HER2-positive breast cancer who have received at most one prior line of systemic therapy (including anti-HER2 treatment) in the advanced setting will be randomized 1:1 to either the experimental or control arm. Stratification factors include ER status and presence of visceral metastases. The primary endpoint is Progression-Free Survival (PFS). Key secondary endpoints include Overall Survival (OS), Objective Response Rate (ORR), Disease Control Rate (DCR), Clinical Benefit Rate (CBR), safety, and patient-reported quality of life. Exploratory endpoints involve correlating circulating tumor cells (CTCs) and PAM50 molecular subtyping with survival outcomes. This study seeks to determine if the all-oral, chemotherapy-free combination is non-inferior to the standard chemo-containing regimen, potentially offering a less toxic and more convenient treatment option for patients with advanced HER2-positive breast cancer.