Pathologic Complete Response (Pcr) Rates After Neoadjuvant Trastuzumab Emtansine (T-Dm1 [K] Pertuzumab (P) Vs Docetaxel Plus Carboplatin Plus Trastuzumab Plus P (Tchp) Treatment In Patients With Her2-Positive (Her2+) Early Breast Cancer (Ebc) (Kristine)

500Background: K and P bind different HER2 domains and have marked antitumor activity in HER2+ breast cancer. KRISTINE (NCT02131064) is an open-label phase 3 study comparing neoadjuvant K + P (KP) vs TCHP in patients with HER2+ EBC. This provides the first phase 3 data for a complete neoadjuvant regimen omitting standard chemotherapy. Methods: The primary endpoint was pCR rate (ypT0/is, ypN0). Treatment-naive women with stage II-IIIC centrally assessed HER2+ EBC were randomized to 6 cycles of KP or TCHP and were then evaluated for pCR. The Cochran Mantel-Haenszel χ2-test stratified by hormone receptor status and clinical stage was used to compare pCR rates. The study had 90% power to detect a 15 percentage point increase in pCR from 60% (TCHP) to 75% (KP). Secondary endpoints included breast conserving surgery (BCS) rate, safety, and patient-reported outcomes. Results: Baseline demographic and disease characteristics were comparable between the TCHP (n = 221) and KP (n = 223) arms. pCR rates were 55.7% (9...