Lapatinib plus trastuzumab in pretreated human epidermal growth factor receptor 2-positive metastatic breast cancer

Background: Dual human epidermal growth factor receptor 2 (HER2) blockade has been preclinically and clinically assessed in HER2-overexpressing metastatic breast cancer (mBC) with encouraging results. Patients and Methods: This is a descriptive retrospective study of trastuzumab plus lapatinib activity in patients with HER2-overexpressing mBC from two centers. The primary endpoints were to assess objective response rate (ORR) and toxicity. The secondary endpoints were to assess progression-free survival (PFS) and overall survival. Results: A total of 23 HER2-positive mBC patients previously treated with trastuzumab received a trastuzumab plus lapatinib based therapy. Chemotherapy (CT) was added to the dual HER2 blockade treatment in 13 patients (56%), whereas hormonotherapy (HT) was added in 8 patients (35%) and 2 patients (9%) received lapatinib plus trastuzumab without any other agent. ORR was 22% (5/23) and 39% (9/23) of patients had stable disease. PFS in the overall population was 4 months. PFS in patients with CT was 5 months, whereas PFS in patients with HT was 2 months. Grade ≥ 3 adverse events were diarrhea (26%) and hand-and-foot syndrome (9%). Conclusions: These findings suggest that dual HER2 blockade in combination with CT is feasible in pretreated HER2-positive mBC patients