Adjuvant trastuzumab emtansine in HER2-positive breast cancer patients with HER2-negative residual invasive disease in KATHERINE
Sibylle Loibl, Chiun‐Sheng Huang, Max S. Mano, Eleftherios P. Mamounas, Charles E. Geyer, Michael Untch, Jean‐Christophe Théry, Ingo Schwaner, Steven Limentani, Niklas Loman, Kristina Lübbe, Jenny C. Chang, Thomas Hatschek, David Tesarowski, Chunyan Song, Sanne Lysbet de Haas, Thomas Boulet, Chiara Lambertini, Norman Wolmark
Abstract
Following chemotherapy and human epidermal growth factor 2 (HER2)-targeted neoadjuvant therapy for HER2-positive early breast cancer, residual invasive breast cancer at surgery may be HER2-negative on retesting in some patients. We evaluated outcomes with T-DM1 and trastuzumab in patients randomized in the phase III KATHERINE trial based on HER2-positive central testing of the pre-treatment core biopsy with HER2-negative central testing on their corresponding surgical specimen after neoadjuvant treatment. In the 70/845 (8.3%) patients with HER2-negative residual disease on retesting at surgery, there were 11 IDFS events in the 42 trastuzumab-treated patients (26.2%) and none in the 28 T-DM1-treated patients, suggesting that T-DM1 should not be withheld in this patient population.