pyrotinib + trastuzumab + dalpiciclib + letrozole

This is a four-drug combination regimen consisting of pyrotinib, trastuzumab, dalpiciclib, and letrozole. Pyrotinib is an oral irreversible tyrosine kinase inhibitor targeting HER2 and EGFR; trastuzumab is a monoclonal antibody against the HER2 receptor; dalpiciclib is an oral cyclin-dependent kinase 4/6 (CDK4/6) inhibitor; and letrozole is a nonsteroidal aromatase inhibitor that suppresses estrogen synthesis. This combination has been investigated as neoadjuvant therapy for triple-positive breast cancer (TPBC), which expresses hormone receptors (HR) and overexpresses HER2. The regimen aims to provide chemotherapy-sparing treatment by simultaneously inhibiting HER2 signaling, cell cycle progression, and estrogen-driven tumor growth. Clinical trials have shown promising pathological response rates with acceptable safety profiles in patients with TPBC[1][2][3].