P2-4-2SAFETY OF TRASTUZUMAB AND PERTUZUMAB FOR PATIENTS WITH PREVIOUSLY TREATED HER2 POSITIVE ADVANCED BREAST CANCER

Abstract Introduction: The double therapy of trastuzumab and pertuzumab (TP) will come into widespread use, because of the beneficial effects on HER2 positive breast cancer. However, we don't have enough information about the safety of TP in Japanese patients. In our hospital, triple therapy of eribulin and TP for previously treated HER2 positive breast cancer is ongoing (UMI12018). In this study, we assessed the safety of TP, including the data of participants in the triple therapy trial. Patients and methods: We assessed the safety of 8 patients who were administered TP in our hospital. Adverse events (AEs) were graded according to CTCAE v4.0. Results: Five patients were administered TP with eribulin, three patients were administered TP without cytotoxic agents. The most common AEs were diarrhea (4 patients), leukopenia (3 patients), neutropenia (3 patients), hypokalemia (3 patients), infusion reaction (3 patients), lymphopenia (2 patients), stomatitis (2 patients), skin disorders (2 patients). Hematologic toxicity, diarrhea, hypokalemia, stomatitis were frequently observed in patients who were administered TP with eribulin. Grade 3 AEs were neutropenia (2 patients), leukopenia (1 patient), lymphopenia (1 patient), pathological fracture (1 patient) and middle otitis (1patient). Grade 4/5 AEs were not observed. Conclusions: The TP therapy would be tolerable for Japanese patients. We will report updated results at the meeting.