ERBB2 and breast cancer: The addition of lapatinib to capecitabine after trastuzumab plus chemotherapy in patients with HER2‐positive breast cancer has advantages in the time to progression (TTP), from 4.4 months in the placebo plus capecitabine group to 8.4 months in the lapatinib plus capecitabine group (HR,0.49; 95%CI: 0.34, 0.71; p < 0.001).151