Corrected QT Interval Effects of Trastuzumab Emtansine (T-DM1) in Patients With Human Epidermal Growth Factor Receptor 2 (HER2)-Positive Locally Advanced or Metastatic Breast Cancer and the Safety and Tolerability of Combined T-DM1 and Pertuzumab in Patients With Early Disease Progression

This is a multicenter, open-label, single-arm Phase II study designed to evaluate the effect of T-DM1 on the duration of corrected QT (QTc) interval in patients with HER2-positive locally advanced or metastatic breast cancer and to make preliminary assessments regarding the safety, tolerability, and efficacy of combined T-DM1 and pertuzumab in patients with early disease progression. The QT interval is a measure of time between the start of the Q wave and the end of the T wave in the heart's electrical cycle. The QTcF interval is the QT interval as calculated using Fridericia's correction; the QTcB interval is the QT interval as calculated using Bazett's correction.