124P Phase Ib-II Neoadjuvant Chemotherapy with Docetaxel Plus Atezolizumab Plus Herceptin SC and Pertuzumab (TAHP) for Patients with HER2-positive Stage II/III Breast Cancer (Neo-Path) (KCSG BR 18-23, NCT03991878)

Preclinical synergy between IO and HER2-directed therapies has been reported. Currently, TCHP (docetaxel + carboplatin + trastuzumab + pertuzumab) regimen are used commonly with the highest pCR rate caused by double HER2 blockade (pCR rate: 60-70%). NCCN guideline recommend it as one of the preferred regimens for neoadjuvant therapy. Although toxicities are manageable, there are considerably higher G3/G4 AEs, including neutropenic fever, neurotoxicity, nephrotoxicity, emesis, and diarrhea. We hypothesized that TAHP without carboplatin but adding atezolizumab instead may have favorable toxicity profile compared with TCHP without compromising clinical outcomes in terms of pCR caused by synergistic effect of atezolizumab + THP.