The standard therapy for primary treatment of HER2-positive metastatic breast cancer (MBC) is combination therapy of pertuzumab (PER), trastuzumab (HER) and docetaxel (DTX). Although the effectiveness of trastuzumab emtansine (T-DM1) after HER treatment has been reported, there are few reports on the effectiveness of T-DM1 for patients treated with PER. We retrospectively investigated the effectiveness of T-DM1 on HER2-positive MBC previously treated with PER.
Between October 2013 and June 2017, 79 patients with HER2-positive MBC were treated with PER. 44 patients were investigated the subsequent treatment. 34 patients received T-DM1, and 10 patients received treatment other than T-DM1 after PER treatment.
Median treatment line was 3.0 (1-9) vs 4.0 (1-9) in the T-DM1 treatment and other than T-DM1 treatment, respectively. The response rate was CR 0% vs 0%, PR 36.0% vs 25%, SD 32.0% vs 62.5%, PD 32.0% vs 12.5%, respectively. The objective response rate was 36.0% vs 20.0%. The clinical benefit rate was 48.0% vs 50.0%. Median time to treatment failure was 6.6 months vs 2.9 months, respectively. There was a significant difference in median overall survival; median not reached vs 19.6 months (p = 0.04).
OS was significantly better with administration of T-DM1 after PER treatment. Based on the results of this study, it was confirmed that efficacy of T-DM1 in patients with HER2-positive metastatic breast cancer previously treated with PER.
Koshi Matsui
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All authors have declared no conflicts of interest.