A report of cardiac events in a phase II clinical study using trastuzumab combined with pertuzumab in HER2-positive metastatic breast cancer (MBC)

1028 Background: T and P are humanized recombinant monoclonal antibodies (MoAB) that target different epitopes of HER2 extracellular domain. P blocks HER2’s ability to heterodimerize with other HER/ErbB receptors. Methods: This Ph II trial evaluates the efficacy and safety of T with P in patients (pts) with HER2+ (FISH +) MBC who had progressive disease (PD) on T-based therapy. Eligible pts must have had = 3 T-based regimens, normal (nl) left ventricular ejection fraction (EF=55%) and without significant cardiac history. Pts received IV T (6mg/kg) and P (420 mg) every 3 weeks (wks). EKG plus echocardiogram (ECHO) or cardiac MRI and tumor response were assessed every 3 and 6 wks, respectively. Results: Eleven pts received 39 (1 to 13) cycles, 1 pt achieved a partial response (PR) and 3 pts had stable disease. A total of 68 ECHOs and 8 cardiac MRIs were performed. Left ventricular systolic dysfunction (LVSD) with nl EKG was seen in 5 pts; Grade (Gr) 1 (n = 2) (EF 50–55%), Gr 2 (n = 2) (EF 40–50%) and Gr 3 (...