Phase II Trial of Pertuzumab and Trastuzumab in Patients With Human Epidermal Growth Factor Receptor 2–Positive Metastatic Breast Cancer That Progressed During Prior Trastuzumab Therapy

All 66 patients were assessable for efficacy and safety. The objective response rate was 24.2%, and the clinical benefit rate was 50%. Five patients (7.6%) experienced a complete response, 11 patients (16.7%) experienced a partial response, and 17 patients (25.8%) experienced stable disease of > or = 6 months. Median progression-free survival was 5.5 months. Overall, the combination of pertuzumab and trastuzumab was well tolerated, and adverse events were mild to moderate. Cardiac dysfunction was minimal, and no patients withdrew as a result of cardiac-related adverse events.

The combination of pertuzumab and trastuzumab is active and well tolerated in patients with metastatic HER2-positive breast cancer who had experienced progression during prior trastuzumab therapy.