Impact of PIK3CA mutation status on immune marker response and pCR in the WSG-ADAPT HER2+/HR+ phase II trial.

572Background: The ADAPT HER2+/HR+ phase II trial (NCT01745965) compared for the first time 12 wks. neoadjuvant T-DM1 (+/- endocrine therapy (ET)) with trastuzumab (T)+ET; pCR (ypT0/is ypN0) was > ...