Eribulin With or Without Trastuzumab-biosimilar in Patients With HER2-overexpressed Recurrent or Stage IV Breast Cancer

HER2-targeted therapy is the mainstay therapeutic option for the treatment of HER2 positive breast cancer patients. Even after progression on HER2-targeted therapy, HER2 remains an effective therapeutic target. In a phase III randomized clinical trial, Lapatinib plus capecitabine showed superior outcome compared to capecitabine alone in HER2 positive breast cancer patients who has progressed after trastuzumab-based therapy Moreover, ado-trastuzumab emtansine (T-DM1) showed improved progression free survival (PFS) and overall survival (OS) in HER2-positive advanced breast cancer patients previously treated with trastuzumab and a taxane. Not only switching to a different HER2-targeted agent, but rechallenge of trastuzumab has also shown efficacy in trastuzumab failed HER2-positive breast cancer patients. In HER2-positive breast cancer patients who failed trastuzumab and lapatinib, rechallenge of trastuzumab in combination with conventional chemotherapy showed response rate of 31%, PFS of 4.9 months, and OS of 19.4 months. Eribulin mesylate is a non-taxane inhibitor of microtubule which shows efficacy in HER2-positive breast cancer. The efficacy of eribulin and trastuzumab combination chemotherapy as first line palliative chemotherapy in HER2-positive breast cancer was identified in a phase II trial. Eribulin plus trastuzumab was an effective regimen which showed response rate of 71.2% and PFS of 11.6 months. Currently, the first line regimen for HER2-positive metastatic breast cancer is combination therapy of pertuzumab, trastuzumab, and docetaxel as a result of the CELOPARTRA trial . After failure on pertuzumab and trastuzumab based combination chemotherapy, T-DM1 is frequently used as a 2nd line therapy. Optimal salvage treatment for HER2-positive breast cancer after trastuzumab and T-DM1 failure still remains to be established. We would like to investigate the efficacy and safety of combination chemotherapy of eribulin and trastuzumab as salvage treatment for HER2-Positive breast cancer after exposure to trastuzumab and T-DM1.