Real-world study of the treatments following trastuzumab-emtansine for HER2-positive metastatic breast cancer: A multicentral cohort study (WJOG12519B).

• DOI: 10.1200/jco.2020.38.15_suppl.e13019
• Publication Date: 2020-05-25T15:16:32Z
• Authors: Sasagu Kurozumi; Takamichi Yokoe; Kazuki Nozawa; Yukinori Ozaki; Tetsuyo Maeda; Shu Yazaki; Mai Onishi; Akihiro Fujimoto; Sayuka Nakayama; Yuko Tsuboguchi; Tsutomu Iwasa; Hitomi Sakai; Misato Ogata; Mitsuo Terada; Meiko Nishimura; Takuma Onoe; Jun Masuda; Michiko Kurikawa; Mototsugu Shimokawa; Toshimi Takano
• Keywords: 03 medical and health sciences; 0302 clinical medicine; 3. Good health

e13019 Background: Since trastuzumab emtansine (T-DM1) was established as a standard treatment option, the treatment strategy of metastatic HER2-positive breast cancer has markedly changed. However, clinical evidence regarding the treatments beyond T-DM1 is insufficient. In this study, we attempted to describe real-world selection and efficacy of treatments following T-DM1 for metastatic HER2-positive breast cancer. Methods: This multi-center retrospective cohort study was conducted in 17 hospitals in Japan. Consecutive patients with metastatic HER2-positive breast cancer who had received T-DM1 and started post-T-DM1 treatments between January 2014 and December 2018 were enrolled. Patients treated with investigational drugs were excluded. The primary endpoint was objective response rate (ORR) of post-T-DM1 treatments. Secondary endpoints included disease control rate (DCR), progression-free survival (PFS), time to treatment failure (TTF), and overall survival (OS). Results: In this study, 325 patients were eligible, of which 182 (56.0%) cases were estrogen receptor-positive and 61 (18.8%) had brain metastases. T-DM1 had been used as the first to 11th (median third) line treatment for metastatic disease. The types of post-T-DM1 treatment were as follows: 1) chemotherapy concomitant with trastuzumab and pertuzumab (n = 102; 31.4%), 2) chemotherapy concomitant with trastuzumab only (n = 78; 24.0%), 3) lapatinib with capecitabine (n = 63; 19.4%), and 4) others (n = 82; 25.2%). ORR of post-T-DM1 treatments was 22.8% (95% confidence interval [CI]: 18.1 to 28.0) and DCR was 66.6% (95% CI: 60.8 to 72.0), calculated with 290 eligible cases with the target lesion. Median PFS was 6.1 months (95%CI: 5.3 to 6.7), median TTF was 5.1 months (95%CI: 4.4 to 5.6), and median OS was 23.7 months (95%CI: 20.7 to 27.4). Conclusions: This real-world study showed that post-T-DM1 treatments had modest anti-tumor activity. Development of more effective treatments beyond T-DM1 is needed for metastatic HER2-positive breast cancer. Clinical trial information: UMIN000037747 .