ERBB2 and breast cancer: KEYNOTE-756 The trial enrolled 1,278 patients with ER+/HER2-, histological grade 3, T1c-T2/cN1-2 or T3-4/cN0-2 breast cancer, with the primary endpoints of pCR (ypT0/Tis, ypN0) and event-free survival (EFS).